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Date:   Thu, 11 Feb 2021 12:00:24 -0700
From:   Mathieu Poirier <mathieu.poirier@linaro.org>
To:     Anshuman Khandual <anshuman.khandual@arm.com>
Cc:     linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org,
        suzuki.poulose@arm.com, mike.leach@linaro.org,
        lcherian@marvell.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V3 11/14] coresight: sink: Add TRBE driver
Message-ID: <20210211190024.GD2186000@xps15>
References: <1611737738-1493-1-git-send-email-anshuman.khandual@arm.com>
 <1611737738-1493-12-git-send-email-anshuman.khandual@arm.com>
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On Wed, Jan 27, 2021 at 02:25:35PM +0530, Anshuman Khandual wrote:
> Trace Buffer Extension (TRBE) implements a trace buffer per CPU which is
> accessible via the system registers. The TRBE supports different addressing
> modes including CPU virtual address and buffer modes including the circular
> buffer mode. The TRBE buffer is addressed by a base pointer (TRBBASER_EL1),
> an write pointer (TRBPTR_EL1) and a limit pointer (TRBLIMITR_EL1). But the
> access to the trace buffer could be prohibited by a higher exception level
> (EL3 or EL2), indicated by TRBIDR_EL1.P. The TRBE can also generate a CPU
> private interrupt (PPI) on address translation errors and when the buffer
> is full. Overall implementation here is inspired from the Arm SPE driver.
> 
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> Changes in V3:
> 
> - Added new DT bindings document TRBE.yaml
> - Changed TRBLIMITR_TRIG_MODE_SHIFT from 2 to 3
> - Dropped isb() from trbe_reset_local()
> - Dropped gap between (void *) and buf->trbe_base
> - Changed 'int' to 'unsigned int' in is_trbe_available()
> - Dropped unused function set_trbe_running(), set_trbe_virtual_mode(),
>   set_trbe_enabled() and set_trbe_limit_pointer()
> - Changed get_trbe_flag_update(), is_trbe_programmable() and
>   get_trbe_address_align() to accept TRBIDR value
> - Changed is_trbe_running(), is_trbe_abort(), is_trbe_wrap(), is_trbe_trg(),
>   is_trbe_irq(), get_trbe_bsc() and get_trbe_ec() to accept TRBSR value
> - Dropped snapshot mode condition in arm_trbe_alloc_buffer()
> - Exit arm_trbe_init() when arm64_kernel_unmapped_at_el0() is enabled
> - Compute trbe_limit before trbe_write to get the updated handle
> - Added trbe_stop_and_truncate_event()
> - Dropped trbe_handle_fatal()
> 
>  Documentation/trace/coresight/coresight-trbe.rst |   39 +
>  arch/arm64/include/asm/sysreg.h                  |    1 +
>  drivers/hwtracing/coresight/Kconfig              |   11 +
>  drivers/hwtracing/coresight/Makefile             |    1 +
>  drivers/hwtracing/coresight/coresight-trbe.c     | 1023 ++++++++++++++++++++++
>  drivers/hwtracing/coresight/coresight-trbe.h     |  160 ++++
>  6 files changed, 1235 insertions(+)
>  create mode 100644 Documentation/trace/coresight/coresight-trbe.rst
>  create mode 100644 drivers/hwtracing/coresight/coresight-trbe.c
>  create mode 100644 drivers/hwtracing/coresight/coresight-trbe.h
> 
> diff --git a/Documentation/trace/coresight/coresight-trbe.rst b/Documentation/trace/coresight/coresight-trbe.rst
> new file mode 100644
> index 0000000..1cbb819
> --- /dev/null
> +++ b/Documentation/trace/coresight/coresight-trbe.rst
> @@ -0,0 +1,39 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +==============================
> +Trace Buffer Extension (TRBE).
> +==============================
> +
> +    :Author:   Anshuman Khandual <anshuman.khandual@arm.com>
> +    :Date:     November 2020
> +
> +Hardware Description
> +--------------------
> +
> +Trace Buffer Extension (TRBE) is a percpu hardware which captures in system
> +memory, CPU traces generated from a corresponding percpu tracing unit. This
> +gets plugged in as a coresight sink device because the corresponding trace
> +genarators (ETE), are plugged in as source device.
> +
> +The TRBE is not compliant to CoreSight architecture specifications, but is
> +driven via the CoreSight driver framework to support the ETE (which is
> +CoreSight compliant) integration.
> +
> +Sysfs files and directories
> +---------------------------
> +
> +The TRBE devices appear on the existing coresight bus alongside the other
> +coresight devices::
> +
> +	>$ ls /sys/bus/coresight/devices
> +	trbe0  trbe1  trbe2 trbe3
> +
> +The ``trbe<N>`` named TRBEs are associated with a CPU.::
> +
> +	>$ ls /sys/bus/coresight/devices/trbe0/
> +        align dbm
> +
> +*Key file items are:-*
> +   * ``align``: TRBE write pointer alignment
> +   * ``dbm``: TRBE updates memory with access and dirty flags
> +
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 85ae4db..9e2e9b7 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -97,6 +97,7 @@
>  #define SET_PSTATE_UAO(x)		__emit_inst(0xd500401f | PSTATE_UAO | ((!!x) << PSTATE_Imm_shift))
>  #define SET_PSTATE_SSBS(x)		__emit_inst(0xd500401f | PSTATE_SSBS | ((!!x) << PSTATE_Imm_shift))
>  #define SET_PSTATE_TCO(x)		__emit_inst(0xd500401f | PSTATE_TCO | ((!!x) << PSTATE_Imm_shift))
> +#define TSB_CSYNC			__emit_inst(0xd503225f)
>  
>  #define set_pstate_pan(x)		asm volatile(SET_PSTATE_PAN(x))
>  #define set_pstate_uao(x)		asm volatile(SET_PSTATE_UAO(x))
> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
> index f154ae7..aa657ab 100644
> --- a/drivers/hwtracing/coresight/Kconfig
> +++ b/drivers/hwtracing/coresight/Kconfig
> @@ -164,6 +164,17 @@ config CORESIGHT_CTI
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called coresight-cti.
>  
> +config CORESIGHT_TRBE
> +	bool "Trace Buffer Extension (TRBE) driver"
> +	depends on ARM64
> +	help
> +	  This driver provides support for percpu Trace Buffer Extension (TRBE).
> +	  TRBE always needs to be used along with it's corresponding percpu ETE
> +	  component. ETE generates trace data which is then captured with TRBE.
> +	  Unlike traditional sink devices, TRBE is a CPU feature accessible via
> +	  system registers. But it's explicit dependency with trace unit (ETE)
> +	  requires it to be plugged in as a coresight sink device.
> +
>  config CORESIGHT_CTI_INTEGRATION_REGS
>  	bool "Access CTI CoreSight Integration Registers"
>  	depends on CORESIGHT_CTI
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index f20e357..d608165 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -21,5 +21,6 @@ obj-$(CONFIG_CORESIGHT_STM) += coresight-stm.o
>  obj-$(CONFIG_CORESIGHT_CPU_DEBUG) += coresight-cpu-debug.o
>  obj-$(CONFIG_CORESIGHT_CATU) += coresight-catu.o
>  obj-$(CONFIG_CORESIGHT_CTI) += coresight-cti.o
> +obj-$(CONFIG_CORESIGHT_TRBE) += coresight-trbe.o
>  coresight-cti-y := coresight-cti-core.o	coresight-cti-platform.o \
>  		   coresight-cti-sysfs.o
> diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
> new file mode 100644
> index 0000000..1464d8b
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-trbe.c
> @@ -0,0 +1,1023 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This driver enables Trace Buffer Extension (TRBE) as a per-cpu coresight
> + * sink device could then pair with an appropriate per-cpu coresight source
> + * device (ETE) thus generating required trace data. Trace can be enabled
> + * via the perf framework.
> + *
> + * Copyright (C) 2020 ARM Ltd.
> + *
> + * Author: Anshuman Khandual <anshuman.khandual@arm.com>
> + */
> +#define DRVNAME "arm_trbe"
> +
> +#define pr_fmt(fmt) DRVNAME ": " fmt
> +
> +#include "coresight-trbe.h"
> +
> +#define PERF_IDX2OFF(idx, buf) ((idx) % ((buf)->nr_pages << PAGE_SHIFT))
> +
> +/*
> + * A padding packet that will help the user space tools
> + * in skipping relevant sections in the captured trace
> + * data which could not be decoded. TRBE doesn't support
> + * formatting the trace data, unlike the legacy CoreSight
> + * sinks and thus we use ETE trace packets to pad the
> + * sections of the buffer.
> + */
> +#define ETE_IGNORE_PACKET 		0x70
> +
> +/*
> + * Minimum amount of meaningful trace will contain:
> + * A-Sync, Trace Info, Trace On, Address, Atom.
> + * This is about 44bytes of ETE trace. To be on
> + * the safer side, we assume 64bytes is the minimum
> + * space required for a meaningful session, before
> + * we hit a "WRAP" event.
> + */
> +#define TRBE_TRACE_MIN_BUF_SIZE		64
> +
> +enum trbe_fault_action {
> +	TRBE_FAULT_ACT_WRAP,
> +	TRBE_FAULT_ACT_SPURIOUS,
> +	TRBE_FAULT_ACT_FATAL,
> +};
> +
> +struct trbe_buf {
> +	unsigned long trbe_base;
> +	unsigned long trbe_limit;
> +	unsigned long trbe_write;
> +	int nr_pages;
> +	void **pages;
> +	bool snapshot;
> +	struct trbe_cpudata *cpudata;
> +};
> +
> +struct trbe_cpudata {
> +	bool trbe_dbm;
> +	u64 trbe_align;
> +	int cpu;
> +	enum cs_mode mode;
> +	struct trbe_buf *buf;
> +	struct trbe_drvdata *drvdata;
> +};
> +
> +struct trbe_drvdata {
> +	struct trbe_cpudata __percpu *cpudata;
> +	struct perf_output_handle __percpu **handle;
> +	struct hlist_node hotplug_node;
> +	int irq;
> +	cpumask_t supported_cpus;
> +	enum cpuhp_state trbe_online;
> +	struct platform_device *pdev;
> +};
> +
> +static int trbe_alloc_node(struct perf_event *event)
> +{
> +	if (event->cpu == -1)
> +		return NUMA_NO_NODE;
> +	return cpu_to_node(event->cpu);
> +}
> +
> +static void trbe_drain_buffer(void)
> +{
> +	asm(TSB_CSYNC);
> +	dsb(nsh);
> +}
> +
> +static void trbe_drain_and_disable_local(void)
> +{
> +	trbe_drain_buffer();
> +	write_sysreg_s(0, SYS_TRBLIMITR_EL1);
> +	isb();
> +}
> +
> +static void trbe_reset_local(void)
> +{
> +	trbe_drain_and_disable_local();
> +	write_sysreg_s(0, SYS_TRBPTR_EL1);
> +	write_sysreg_s(0, SYS_TRBBASER_EL1);
> +	write_sysreg_s(0, SYS_TRBSR_EL1);
> +}
> +
> +static void trbe_stop_and_truncate_event(struct perf_output_handle *handle)
> +{
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +
> +	/*
> +	 * We cannot proceed with the buffer collection and we
> +	 * do not have any data for the current session. The
> +	 * etm_perf driver expects to close out the aux_buffer
> +	 * at event_stop(). So disable the TRBE here and leave
> +	 * the update_buffer() to return a 0 size.
> +	 */
> +	trbe_drain_and_disable_local();
> +	perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> +	*this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL;
> +}
> +
> +/*
> + * TRBE Buffer Management
> + *
> + * The TRBE buffer spans from the base pointer till the limit pointer. When enabled,
> + * it starts writing trace data from the write pointer onward till the limit pointer.
> + * When the write pointer reaches the address just before the limit pointer, it gets
> + * wrapped around again to the base pointer. This is called a TRBE wrap event, which
> + * generates a maintenance interrupt when operated in WRAP or FILL mode. This driver
> + * uses FILL mode, where the TRBE stops the trace collection at wrap event. The IRQ
> + * handler updates the AUX buffer and re-enables the TRBE with updated WRITE and
> + * LIMIT pointers.
> + *
> + *	Wrap around with an IRQ
> + *	------ < ------ < ------- < ----- < -----
> + *	|					|
> + *	------ > ------ > ------- > ----- > -----
> + *
> + *	+---------------+-----------------------+
> + *	|		|			|
> + *	+---------------+-----------------------+
> + *	Base Pointer	Write Pointer		Limit Pointer
> + *
> + * The base and limit pointers always needs to be PAGE_SIZE aligned. But the write
> + * pointer can be aligned to the implementation defined TRBE trace buffer alignment
> + * as captured in trbe_cpudata->trbe_align.
> + *
> + *
> + *		head		tail		wakeup
> + *	+---------------------------------------+----- ~ ~ ------
> + *	|$$$$$$$|################|$$$$$$$$$$$$$$|		|
> + *	+---------------------------------------+----- ~ ~ ------
> + *	Base Pointer	Write Pointer		Limit Pointer
> + *
> + * The perf_output_handle indices (head, tail, wakeup) are monotonically increasing
> + * values which tracks all the driver writes and user reads from the perf auxiliary
> + * buffer. Generally [head..tail] is the area where the driver can write into unless
> + * the wakeup is behind the tail. Enabled TRBE buffer span needs to be adjusted and
> + * configured depending on the perf_output_handle indices, so that the driver does
> + * not override into areas in the perf auxiliary buffer which is being or yet to be
> + * consumed from the user space. The enabled TRBE buffer area is a moving subset of
> + * the allocated perf auxiliary buffer.
> + */
> +static void trbe_pad_buf(struct perf_output_handle *handle, int len)
> +{
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +	u64 head = PERF_IDX2OFF(handle->head, buf);
> +
> +	memset((void *)buf->trbe_base + head, ETE_IGNORE_PACKET, len);
> +	if (!buf->snapshot)
> +		perf_aux_output_skip(handle, len);
> +}
> +
> +static unsigned long trbe_snapshot_offset(struct perf_output_handle *handle)
> +{
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +
> +	/*
> +	 * The ETE trace has alignment synchronization packets allowing
> +	 * the decoder to reset in case of an overflow or corruption.
> +	 * So we can use the entire buffer for the snapshot mode.
> +	 */
> +	return buf->nr_pages * PAGE_SIZE;
> +}
> +
> +/*
> + * TRBE Limit Calculation
> + *
> + * The following markers are used to illustrate various TRBE buffer situations.
> + *
> + * $$$$ - Data area, unconsumed captured trace data, not to be overridden
> + * #### - Free area, enabled, trace will be written
> + * %%%% - Free area, disabled, trace will not be written
> + * ==== - Free area, padded with ETE_IGNORE_PACKET, trace will be skipped
> + */
> +static unsigned long __trbe_normal_offset(struct perf_output_handle *handle)
> +{
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +	struct trbe_cpudata *cpudata = buf->cpudata;
> +	const u64 bufsize = buf->nr_pages * PAGE_SIZE;
> +	u64 limit = bufsize;
> +	u64 head, tail, wakeup;
> +
> +	head = PERF_IDX2OFF(handle->head, buf);
> +
> +	/*
> +	 *		head
> +	 *	------->|
> +	 *	|
> +	 *	head	TRBE align	tail
> +	 * +----|-------|---------------|-------+
> +	 * |$$$$|=======|###############|$$$$$$$|
> +	 * +----|-------|---------------|-------+
> +	 * trbe_base				trbe_base + nr_pages
> +	 *
> +	 * Perf aux buffer output head position can be misaligned depending on
> +	 * various factors including user space reads. In case misaligned, head
> +	 * needs to be aligned before TRBE can be configured. Pad the alignment
> +	 * gap with ETE_IGNORE_PACKET bytes that will be ignored by user tools
> +	 * and skip this section thus advancing the head.
> +	 */
> +	if (!IS_ALIGNED(head, cpudata->trbe_align)) {
> +		unsigned long delta = roundup(head, cpudata->trbe_align) - head;
> +
> +		delta = min(delta, handle->size);
> +		trbe_pad_buf(handle, delta);
> +		head = PERF_IDX2OFF(handle->head, buf);
> +	}
> +
> +	/*
> +	 *	head = tail (size = 0)
> +	 * +----|-------------------------------+
> +	 * |$$$$|$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$	|
> +	 * +----|-------------------------------+
> +	 * trbe_base				trbe_base + nr_pages
> +	 *
> +	 * Perf aux buffer does not have any space for the driver to write into.
> +	 * Just communicate trace truncation event to the user space by marking
> +	 * it with PERF_AUX_FLAG_TRUNCATED.
> +	 */
> +	if (!handle->size) {
> +		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> +		return 0;
> +	}
> +
> +	/* Compute the tail and wakeup indices now that we've aligned head */
> +	tail = PERF_IDX2OFF(handle->head + handle->size, buf);
> +	wakeup = PERF_IDX2OFF(handle->wakeup, buf);
> +
> +	/*
> +	 * Lets calculate the buffer area which TRBE could write into. There
> +	 * are three possible scenarios here. Limit needs to be aligned with
> +	 * PAGE_SIZE per the TRBE requirement. Always avoid clobbering the
> +	 * unconsumed data.
> +	 *
> +	 * 1) head < tail
> +	 *
> +	 *	head			tail
> +	 * +----|-----------------------|-------+
> +	 * |$$$$|#######################|$$$$$$$|
> +	 * +----|-----------------------|-------+
> +	 * trbe_base			limit	trbe_base + nr_pages
> +	 *
> +	 * TRBE could write into [head..tail] area. Unless the tail is right at
> +	 * the end of the buffer, neither an wrap around nor an IRQ is expected
> +	 * while being enabled.
> +	 *
> +	 * 2) head == tail
> +	 *
> +	 *	head = tail (size > 0)
> +	 * +----|-------------------------------+
> +	 * |%%%%|###############################|
> +	 * +----|-------------------------------+
> +	 * trbe_base				limit = trbe_base + nr_pages
> +	 *
> +	 * TRBE should just write into [head..base + nr_pages] area even though
> +	 * the entire buffer is empty. Reason being, when the trace reaches the
> +	 * end of the buffer, it will just wrap around with an IRQ giving an
> +	 * opportunity to reconfigure the buffer.
> +	 *
> +	 * 3) tail < head
> +	 *
> +	 *	tail			head
> +	 * +----|-----------------------|-------+
> +	 * |%%%%|$$$$$$$$$$$$$$$$$$$$$$$|#######|
> +	 * +----|-----------------------|-------+
> +	 * trbe_base				limit = trbe_base + nr_pages
> +	 *
> +	 * TRBE should just write into [head..base + nr_pages] area even though
> +	 * the [trbe_base..tail] is also empty. Reason being, when the trace
> +	 * reaches the end of the buffer, it will just wrap around with an IRQ
> +	 * giving an opportunity to reconfigure the buffer.
> +	 */
> +	if (head < tail)
> +		limit = round_down(tail, PAGE_SIZE);
> +
> +	/*
> +	 * Wakeup may be arbitrarily far into the future. If it's not in the
> +	 * current generation, either we'll wrap before hitting it, or it's
> +	 * in the past and has been handled already.
> +	 *
> +	 * If there's a wakeup before we wrap, arrange to be woken up by the
> +	 * page boundary following it. Keep the tail boundary if that's lower.
> +	 *
> +	 *	head		wakeup	tail
> +	 * +----|---------------|-------|-------+
> +	 * |$$$$|###############|%%%%%%%|$$$$$$$|
> +	 * +----|---------------|-------|-------+
> +	 * trbe_base		limit		trbe_base + nr_pages
> +	 */
> +	if (handle->wakeup < (handle->head + handle->size) && head <= wakeup)
> +		limit = min(limit, round_up(wakeup, PAGE_SIZE));
> +
> +	/*
> +	 * There are two situation when this can happen i.e limit is before
> +	 * the head and hence TRBE cannot be configured.
> +	 *
> +	 * 1) head < tail (aligned down with PAGE_SIZE) and also they are both
> +	 * within the same PAGE size range.
> +	 *
> +	 *			PAGE_SIZE
> +	 *		|----------------------|
> +	 *
> +	 *		limit	head	tail
> +	 * +------------|------|--------|-------+
> +	 * |$$$$$$$$$$$$$$$$$$$|========|$$$$$$$|
> +	 * +------------|------|--------|-------+
> +	 * trbe_base				trbe_base + nr_pages
> +	 *
> +	 * 2) head < wakeup (aligned up with PAGE_SIZE) < tail and also both
> +	 * head and wakeup are within same PAGE size range.
> +	 *
> +	 *		PAGE_SIZE
> +	 *	|----------------------|
> +	 *
> +	 *	limit	head	wakeup  tail
> +	 * +----|------|-------|--------|-------+
> +	 * |$$$$$$$$$$$|=======|========|$$$$$$$|
> +	 * +----|------|-------|--------|-------+
> +	 * trbe_base				trbe_base + nr_pages
> +	 */
> +	if (limit > head)
> +		return limit;
> +
> +	trbe_pad_buf(handle, handle->size);
> +	perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> +	return 0;
> +}
> +
> +static unsigned long trbe_normal_offset(struct perf_output_handle *handle)
> +{
> +	struct trbe_buf *buf = perf_get_aux(handle);
> +	u64 limit = __trbe_normal_offset(handle);
> +	u64 head = PERF_IDX2OFF(handle->head, buf);
> +
> +	/*
> +	 * If the head is too close to the limit and we don't
> +	 * have space for a meaningful run, we rather pad it
> +	 * and start fresh.
> +	 */
> +	if (limit && (limit - head < TRBE_TRACE_MIN_BUF_SIZE)) {
> +		trbe_pad_buf(handle, limit - head);
> +		limit = __trbe_normal_offset(handle);
> +	}
> +	return limit;
> +}
> +
> +static unsigned long compute_trbe_buffer_limit(struct perf_output_handle *handle)
> +{
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +	unsigned long offset;
> +
> +	if (buf->snapshot)
> +		offset = trbe_snapshot_offset(handle);
> +	else
> +		offset = trbe_normal_offset(handle);
> +	return buf->trbe_base + offset;
> +}
> +
> +static void clr_trbe_status(void)
> +{
> +	u64 trbsr = read_sysreg_s(SYS_TRBSR_EL1);
> +
> +	WARN_ON(is_trbe_enabled());
> +	trbsr &= ~TRBSR_IRQ;
> +	trbsr &= ~TRBSR_TRG;
> +	trbsr &= ~TRBSR_WRAP;
> +	trbsr &= ~(TRBSR_EC_MASK << TRBSR_EC_SHIFT);
> +	trbsr &= ~(TRBSR_BSC_MASK << TRBSR_BSC_SHIFT);
> +	trbsr &= ~TRBSR_STOP;
> +	write_sysreg_s(trbsr, SYS_TRBSR_EL1);
> +}
> +
> +static void set_trbe_limit_pointer_enabled(unsigned long addr)
> +{
> +	u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);
> +
> +	WARN_ON(!IS_ALIGNED(addr, (1UL << TRBLIMITR_LIMIT_SHIFT)));
> +	WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));
> +
> +	trblimitr &= ~TRBLIMITR_NVM;
> +	trblimitr &= ~(TRBLIMITR_FILL_MODE_MASK << TRBLIMITR_FILL_MODE_SHIFT);
> +	trblimitr &= ~(TRBLIMITR_TRIG_MODE_MASK << TRBLIMITR_TRIG_MODE_SHIFT);
> +	trblimitr &= ~(TRBLIMITR_LIMIT_MASK << TRBLIMITR_LIMIT_SHIFT);
> +
> +	/*
> +	 * Fill trace buffer mode is used here while configuring the
> +	 * TRBE for trace capture. In this particular mode, the trace
> +	 * collection is stopped and a maintenance interrupt is raised
> +	 * when the current write pointer wraps. This pause in trace
> +	 * collection gives the software an opportunity to capture the
> +	 * trace data in the interrupt handler, before reconfiguring
> +	 * the TRBE.
> +	 */
> +	trblimitr |= (TRBE_FILL_MODE_FILL & TRBLIMITR_FILL_MODE_MASK) << TRBLIMITR_FILL_MODE_SHIFT;
> +
> +	/*
> +	 * Trigger mode is not used here while configuring the TRBE for
> +	 * the trace capture. Hence just keep this in the ignore mode.
> +	 */
> +	trblimitr |= (TRBE_TRIG_MODE_IGNORE & TRBLIMITR_TRIG_MODE_MASK) << TRBLIMITR_TRIG_MODE_SHIFT;
> +	trblimitr |= (addr & PAGE_MASK);
> +
> +	trblimitr |= TRBLIMITR_ENABLE;
> +	write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);
> +}
> +
> +static void trbe_enable_hw(struct trbe_buf *buf)
> +{
> +	WARN_ON(buf->trbe_write < buf->trbe_base);
> +	WARN_ON(buf->trbe_write >= buf->trbe_limit);
> +	set_trbe_disabled();
> +	isb();
> +	clr_trbe_status();
> +	set_trbe_base_pointer(buf->trbe_base);
> +	set_trbe_write_pointer(buf->trbe_write);
> +
> +	/*
> +	 * Synchronize all the register updates
> +	 * till now before enabling the TRBE.
> +	 */
> +	isb();
> +	set_trbe_limit_pointer_enabled(buf->trbe_limit);
> +
> +	/* Synchronize the TRBE enable event */
> +	isb();
> +}
> +
> +static void *arm_trbe_alloc_buffer(struct coresight_device *csdev,
> +				   struct perf_event *event, void **pages,
> +				   int nr_pages, bool snapshot)
> +{
> +	struct trbe_buf *buf;
> +	struct page **pglist;
> +	int i;
> +
> +	/*
> +	 * TRBE LIMIT and TRBE WRITE pointers must be page aligned. But with
> +	 * just a single page, there is not much room left while writing into
> +	 * a partially filled TRBE buffer. Hence restrict the minimum buffer
> +	 * size as two pages.
> +	 */

I read this three times and event then I'm not sure to fully get it.  I
suggest re-working this paragraph.


> +	if (nr_pages < 2)
> +		return NULL;
> +
> +	buf = kzalloc_node(sizeof(*buf), GFP_KERNEL, trbe_alloc_node(event));
> +	if (IS_ERR(buf))
> +		return ERR_PTR(-ENOMEM);
> +
> +	pglist = kcalloc(nr_pages, sizeof(*pglist), GFP_KERNEL);
> +	if (IS_ERR(pglist)) {
> +		kfree(buf);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	for (i = 0; i < nr_pages; i++)
> +		pglist[i] = virt_to_page(pages[i]);
> +
> +	buf->trbe_base = (unsigned long) vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL);
> +	if (IS_ERR((void *)buf->trbe_base)) {

Why not simply make buf->trbe_base a void * instead of having to do all this
casting?  And IS_ERR() doesn't work with vmap().

> +		kfree(pglist);
> +		kfree(buf);
> +		return ERR_PTR(buf->trbe_base);
> +	}
> +	buf->trbe_limit = buf->trbe_base + nr_pages * PAGE_SIZE;
> +	buf->trbe_write = buf->trbe_base;
> +	buf->snapshot = snapshot;
> +	buf->nr_pages = nr_pages;
> +	buf->pages = pages;
> +	kfree(pglist);
> +	return buf;
> +}
> +
> +void arm_trbe_free_buffer(void *config)
> +{
> +	struct trbe_buf *buf = config;
> +
> +	vunmap((void *)buf->trbe_base);
> +	kfree(buf);
> +}
> +
> +static unsigned long arm_trbe_update_buffer(struct coresight_device *csdev,
> +					    struct perf_output_handle *handle,
> +					    void *config)
> +{
> +	struct trbe_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	struct trbe_cpudata *cpudata = dev_get_drvdata(&csdev->dev);
> +	struct trbe_buf *buf = config;
> +	unsigned long size, offset;
> +
> +	WARN_ON(buf->cpudata != cpudata);
> +	WARN_ON(cpudata->cpu != smp_processor_id());
> +	WARN_ON(cpudata->drvdata != drvdata);
> +	if (cpudata->mode != CS_MODE_PERF)
> +		return -EINVAL;
> +
> +	/*
> +	 * If the TRBE was disabled due to lack of space in the AUX buffer or a
> +	 * spurious fault, the driver leaves it disabled, truncating the buffer.
> +	 * Since the etm_perf driver expects to close out the AUX buffer, the
> +	 * driver skips it. Thus, just pass in 0 size here to indicate that the
> +	 * buffer was truncated.
> +	 */
> +	if (!is_trbe_enabled())
> +		return 0;
> +	/*
> +	 * perf handle structure needs to be shared with the TRBE IRQ handler for
> +	 * capturing trace data and restarting the handle. There is a probability
> +	 * of an undefined reference based crash when etm event is being stopped
> +	 * while a TRBE IRQ also getting processed. This happens due the release
> +	 * of perf handle via perf_aux_output_end() in etm_event_stop(). Stopping
> +	 * the TRBE here will ensure that no IRQ could be generated when the perf
> +	 * handle gets freed in etm_event_stop().
> +	 */
> +	trbe_drain_and_disable_local();
> +	offset = get_trbe_write_pointer() - get_trbe_base_pointer();
> +	size = offset - PERF_IDX2OFF(handle->head, buf);
> +	if (buf->snapshot)
> +		handle->head += size;
> +	return size;
> +}
> +
> +static int arm_trbe_enable(struct coresight_device *csdev, u32 mode, void *data)
> +{
> +	struct trbe_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	struct trbe_cpudata *cpudata = dev_get_drvdata(&csdev->dev);
> +	struct perf_output_handle *handle = data;
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +
> +	WARN_ON(cpudata->cpu != smp_processor_id());
> +	WARN_ON(cpudata->drvdata != drvdata);
> +	if (mode != CS_MODE_PERF)
> +		return -EINVAL;
> +
> +	*this_cpu_ptr(drvdata->handle) = handle;
> +	cpudata->buf = buf;
> +	cpudata->mode = mode;
> +	buf->cpudata = cpudata;
> +	buf->trbe_limit = compute_trbe_buffer_limit(handle);
> +	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
> +	if (buf->trbe_limit == buf->trbe_base) {
> +		trbe_stop_and_truncate_event(handle);
> +		return 0;
> +	}
> +	trbe_enable_hw(buf);
> +	return 0;
> +}
> +
> +static int arm_trbe_disable(struct coresight_device *csdev)
> +{
> +	struct trbe_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +	struct trbe_cpudata *cpudata = dev_get_drvdata(&csdev->dev);
> +	struct trbe_buf *buf = cpudata->buf;
> +
> +	WARN_ON(buf->cpudata != cpudata);
> +	WARN_ON(cpudata->cpu != smp_processor_id());
> +	WARN_ON(cpudata->drvdata != drvdata);
> +	if (cpudata->mode != CS_MODE_PERF)
> +		return -EINVAL;
> +
> +	trbe_drain_and_disable_local();
> +	buf->cpudata = NULL;
> +	cpudata->buf = NULL;
> +	cpudata->mode = CS_MODE_DISABLED;
> +	return 0;
> +}
> +
> +static void trbe_handle_spurious(struct perf_output_handle *handle)
> +{
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +
> +	buf->trbe_limit = compute_trbe_buffer_limit(handle);
> +	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
> +	if (buf->trbe_limit == buf->trbe_base) {
> +		trbe_drain_and_disable_local();
> +		return;
> +	}
> +	trbe_enable_hw(buf);
> +}
> +
> +static void trbe_handle_overflow(struct perf_output_handle *handle)
> +{
> +	struct perf_event *event = handle->event;
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +	unsigned long offset, size;
> +	struct etm_event_data *event_data;
> +
> +	offset = get_trbe_limit_pointer() - get_trbe_base_pointer();
> +	size = offset - PERF_IDX2OFF(handle->head, buf);
> +	if (buf->snapshot)
> +		handle->head = offset;
> +	perf_aux_output_end(handle, size);
> +
> +	event_data = perf_aux_output_begin(handle, event);
> +	if (!event_data) {
> +		trbe_drain_and_disable_local();
> +		*this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL;
> +		return;
> +	}
> +	buf->trbe_limit = compute_trbe_buffer_limit(handle);
> +	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
> +	if (buf->trbe_limit == buf->trbe_base) {
> +		trbe_stop_and_truncate_event(handle);
> +		return;
> +	}
> +	*this_cpu_ptr(buf->cpudata->drvdata->handle) = handle;
> +	trbe_enable_hw(buf);
> +}
> +
> +static bool is_perf_trbe(struct perf_output_handle *handle)
> +{
> +	struct trbe_buf *buf = etm_perf_sink_config(handle);
> +	struct trbe_cpudata *cpudata = buf->cpudata;
> +	struct trbe_drvdata *drvdata = cpudata->drvdata;
> +	int cpu = smp_processor_id();
> +
> +	WARN_ON(buf->trbe_base != get_trbe_base_pointer());
> +	WARN_ON(buf->trbe_limit != get_trbe_limit_pointer());
> +
> +	if (cpudata->mode != CS_MODE_PERF)
> +		return false;
> +
> +	if (cpudata->cpu != cpu)
> +		return false;
> +
> +	if (!cpumask_test_cpu(cpu, &drvdata->supported_cpus))
> +		return false;
> +
> +	return true;
> +}
> +
> +static enum trbe_fault_action trbe_get_fault_act(struct perf_output_handle *handle)
> +{
> +	u64 trbsr = read_sysreg_s(SYS_TRBSR_EL1);
> +	int ec = get_trbe_ec(trbsr);
> +	int bsc = get_trbe_bsc(trbsr);
> +
> +	WARN_ON(is_trbe_running(trbsr));
> +	if (is_trbe_trg(trbsr) || is_trbe_abort(trbsr))
> +		return TRBE_FAULT_ACT_FATAL;
> +
> +	if ((ec == TRBE_EC_STAGE1_ABORT) || (ec == TRBE_EC_STAGE2_ABORT))
> +		return TRBE_FAULT_ACT_FATAL;
> +
> +	if (is_trbe_wrap(trbsr) && (ec == TRBE_EC_OTHERS) && (bsc == TRBE_BSC_FILLED)) {
> +		if (get_trbe_write_pointer() == get_trbe_base_pointer())
> +			return TRBE_FAULT_ACT_WRAP;
> +	}
> +	return TRBE_FAULT_ACT_SPURIOUS;
> +}
> +
> +static irqreturn_t arm_trbe_irq_handler(int irq, void *dev)
> +{
> +	struct perf_output_handle **handle_ptr = dev;
> +	struct perf_output_handle *handle = *handle_ptr;
> +	enum trbe_fault_action act;
> +
> +	WARN_ON(!is_trbe_irq(read_sysreg_s(SYS_TRBSR_EL1)));
> +	clr_trbe_irq();
> +
> +	/*
> +	 * Ensure the trace is visible to the CPUs and
> +	 * any external aborts have been resolved.
> +	 */
> +	trbe_drain_buffer();
> +	isb();
> +
> +	if (!perf_get_aux(handle))
> +		return IRQ_NONE;
> +
> +	if (!is_perf_trbe(handle))
> +		return IRQ_NONE;
> +
> +	irq_work_run();
> +
> +	act = trbe_get_fault_act(handle);
> +	switch (act) {
> +	case TRBE_FAULT_ACT_WRAP:
> +		trbe_handle_overflow(handle);
> +		break;
> +	case TRBE_FAULT_ACT_SPURIOUS:
> +		trbe_handle_spurious(handle);
> +		break;
> +	case TRBE_FAULT_ACT_FATAL:
> +		trbe_stop_and_truncate_event(handle);
> +		break;
> +	}
> +	return IRQ_HANDLED;
> +}
> +
> +static const struct coresight_ops_sink arm_trbe_sink_ops = {
> +	.enable		= arm_trbe_enable,
> +	.disable	= arm_trbe_disable,
> +	.alloc_buffer	= arm_trbe_alloc_buffer,
> +	.free_buffer	= arm_trbe_free_buffer,
> +	.update_buffer	= arm_trbe_update_buffer,
> +};
> +
> +static const struct coresight_ops arm_trbe_cs_ops = {
> +	.sink_ops	= &arm_trbe_sink_ops,
> +};
> +
> +static ssize_t align_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct trbe_cpudata *cpudata = dev_get_drvdata(dev);
> +
> +	return sprintf(buf, "%llx\n", cpudata->trbe_align);
> +}
> +static DEVICE_ATTR_RO(align);
> +
> +static ssize_t dbm_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct trbe_cpudata *cpudata = dev_get_drvdata(dev);
> +
> +	return sprintf(buf, "%d\n", cpudata->trbe_dbm);
> +}
> +static DEVICE_ATTR_RO(dbm);

What does "dbm" stand for?  Looking at the documentation for TRBIDR_EL1.F, I
don't see what "dbm" relates to.

> +
> +static struct attribute *arm_trbe_attrs[] = {
> +	&dev_attr_align.attr,
> +	&dev_attr_dbm.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group arm_trbe_group = {
> +	.attrs = arm_trbe_attrs,
> +};
> +
> +static const struct attribute_group *arm_trbe_groups[] = {
> +	&arm_trbe_group,
> +	NULL,
> +};
> +
> +static void arm_trbe_probe_coresight_cpu(void *info)
> +{
> +	struct trbe_drvdata *drvdata = info;
> +	struct coresight_desc desc = { 0 };
> +	int cpu = smp_processor_id();
> +	struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
> +	struct coresight_device *trbe_csdev = per_cpu(csdev_sink, cpu);
> +	u64 trbidr = read_sysreg_s(SYS_TRBIDR_EL1);
> +	struct device *dev;
> +
> +	if (WARN_ON(!cpudata))
> +		goto cpu_clear;
> +
> +	if (trbe_csdev)
> +		return;
> +
> +	cpudata->cpu = smp_processor_id();
> +	cpudata->drvdata = drvdata;
> +	dev = &cpudata->drvdata->pdev->dev;
> +
> +	if (!is_trbe_available()) {
> +		pr_err("TRBE is not implemented on cpu %d\n", cpudata->cpu);
> +		goto cpu_clear;
> +	}
> +
> +	if (!is_trbe_programmable(trbidr)) {
> +		pr_err("TRBE is owned in higher exception level on cpu %d\n", cpudata->cpu);
> +		goto cpu_clear;
> +	}
> +	desc.name = devm_kasprintf(dev, GFP_KERNEL, "%s%d", DRVNAME, smp_processor_id());
> +	if (IS_ERR(desc.name))
> +		goto cpu_clear;
> +
> +	desc.type = CORESIGHT_DEV_TYPE_SINK;
> +	desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM;
> +	desc.ops = &arm_trbe_cs_ops;
> +	desc.pdata = dev_get_platdata(dev);
> +	desc.groups = arm_trbe_groups;
> +	desc.dev = dev;
> +	trbe_csdev = coresight_register(&desc);
> +	if (IS_ERR(trbe_csdev))
> +		goto cpu_clear;
> +
> +	dev_set_drvdata(&trbe_csdev->dev, cpudata);
> +	cpudata->trbe_dbm = get_trbe_flag_update(trbidr);
> +	cpudata->trbe_align = 1ULL << get_trbe_address_align(trbidr);
> +	if (cpudata->trbe_align > SZ_2K) {
> +		pr_err("Unsupported alignment on cpu %d\n", cpudata->cpu);
> +		goto cpu_clear;
> +	}
> +	per_cpu(csdev_sink, cpu) = trbe_csdev;
> +	trbe_reset_local();
> +	enable_percpu_irq(drvdata->irq, IRQ_TYPE_NONE);
> +	return;
> +cpu_clear:
> +	cpumask_clear_cpu(cpudata->cpu, &cpudata->drvdata->supported_cpus);
> +}
> +
> +static void arm_trbe_remove_coresight_cpu(void *info)
> +{
> +	int cpu = smp_processor_id();
> +	struct trbe_drvdata *drvdata = info;
> +	struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
> +	struct coresight_device *trbe_csdev = per_cpu(csdev_sink, cpu);
> +
> +	if (trbe_csdev) {
> +		coresight_unregister(trbe_csdev);
> +		cpudata->drvdata = NULL;
> +		per_cpu(csdev_sink, cpu) = NULL;
> +	}
> +	disable_percpu_irq(drvdata->irq);
> +	trbe_reset_local();
> +}
> +
> +static int arm_trbe_probe_coresight(struct trbe_drvdata *drvdata)
> +{
> +	drvdata->cpudata = alloc_percpu(typeof(*drvdata->cpudata));
> +	if (IS_ERR(drvdata->cpudata))
> +		return PTR_ERR(drvdata->cpudata);
> +
> +	arm_trbe_probe_coresight_cpu(drvdata);
> +	smp_call_function_many(&drvdata->supported_cpus, arm_trbe_probe_coresight_cpu, drvdata, 1);
> +	return 0;
> +}
> +
> +static int arm_trbe_remove_coresight(struct trbe_drvdata *drvdata)
> +{
> +	arm_trbe_remove_coresight_cpu(drvdata);
> +	smp_call_function_many(&drvdata->supported_cpus, arm_trbe_remove_coresight_cpu, drvdata, 1);
> +	free_percpu(drvdata->cpudata);
> +	return 0;
> +}
> +
> +static int arm_trbe_cpu_startup(unsigned int cpu, struct hlist_node *node)
> +{
> +	struct trbe_drvdata *drvdata = hlist_entry_safe(node, struct trbe_drvdata, hotplug_node);
> +
> +	if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) {
> +		if (!per_cpu(csdev_sink, cpu)) {
> +			arm_trbe_probe_coresight_cpu(drvdata);
> +		} else {
> +			trbe_reset_local();
> +			enable_percpu_irq(drvdata->irq, IRQ_TYPE_NONE);
> +		}
> +	}
> +	return 0;
> +}
> +
> +static int arm_trbe_cpu_teardown(unsigned int cpu, struct hlist_node *node)
> +{
> +	struct trbe_drvdata *drvdata = hlist_entry_safe(node, struct trbe_drvdata, hotplug_node);
> +
> +	if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) {
> +		disable_percpu_irq(drvdata->irq);
> +		trbe_reset_local();
> +	}
> +	return 0;
> +}
> +
> +static int arm_trbe_probe_cpuhp(struct trbe_drvdata *drvdata)
> +{
> +	enum cpuhp_state trbe_online;
> +
> +	trbe_online = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, DRVNAME,
> +					arm_trbe_cpu_startup, arm_trbe_cpu_teardown);

Indentation

        trbe_online = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, DRVNAME,
                                              arm_trbe_cpu_startup,
                                              arm_trbe_cpu_teardown);

> +	if (trbe_online < 0)
> +		return -EINVAL

Wrong error code 

> +
> +	if (cpuhp_state_add_instance(trbe_online, &drvdata->hotplug_node))
> +		return -EINVAL;

Wrong error code. Even if the callbacks aren't called it might be a good idea to
properly cleanup the with cpuhp_remove_multi_state().

More to come tomorrow.

Thanks,
Mathieu

> +
> +	drvdata->trbe_online = trbe_online;
> +	return 0;
> +}
> +
> +static void arm_trbe_remove_cpuhp(struct trbe_drvdata *drvdata)
> +{
> +	cpuhp_remove_multi_state(drvdata->trbe_online);
> +}
> +
> +static int arm_trbe_probe_irq(struct platform_device *pdev,
> +			      struct trbe_drvdata *drvdata)
> +{
> +	drvdata->irq = platform_get_irq(pdev, 0);
> +	if (!drvdata->irq) {
> +		pr_err("IRQ not found for the platform device\n");
> +		return -ENXIO;
> +	}
> +
> +	if (!irq_is_percpu(drvdata->irq)) {
> +		pr_err("IRQ is not a PPI\n");
> +		return -EINVAL;
> +	}
> +
> +	if (irq_get_percpu_devid_partition(drvdata->irq, &drvdata->supported_cpus))
> +		return -EINVAL;
> +
> +	drvdata->handle = alloc_percpu(typeof(*drvdata->handle));
> +	if (!drvdata->handle)
> +		return -ENOMEM;
> +
> +	if (request_percpu_irq(drvdata->irq, arm_trbe_irq_handler, DRVNAME, drvdata->handle)) {
> +		free_percpu(drvdata->handle);
> +		return -EINVAL;
> +	}
> +	return 0;
> +}
> +
> +static void arm_trbe_remove_irq(struct trbe_drvdata *drvdata)
> +{
> +	free_percpu_irq(drvdata->irq, drvdata->handle);
> +	free_percpu(drvdata->handle);
> +}
> +
> +static int arm_trbe_device_probe(struct platform_device *pdev)
> +{
> +	struct coresight_platform_data *pdata;
> +	struct trbe_drvdata *drvdata;
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> +	if (IS_ERR(drvdata))
> +		return -ENOMEM;
> +
> +	pdata = coresight_get_platform_data(dev);
> +	if (IS_ERR(pdata)) {
> +		kfree(drvdata);
> +		return -ENOMEM;
> +	}
> +
> +	dev_set_drvdata(dev, drvdata);
> +	dev->platform_data = pdata;
> +	drvdata->pdev = pdev;
> +	ret = arm_trbe_probe_irq(pdev, drvdata);
> +	if (ret)
> +		goto irq_failed;
> +
> +	ret = arm_trbe_probe_coresight(drvdata);
> +	if (ret)
> +		goto probe_failed;
> +
> +	ret = arm_trbe_probe_cpuhp(drvdata);
> +	if (ret)
> +		goto cpuhp_failed;
> +
> +	return 0;
> +cpuhp_failed:
> +	arm_trbe_remove_coresight(drvdata);
> +probe_failed:
> +	arm_trbe_remove_irq(drvdata);
> +irq_failed:
> +	kfree(pdata);
> +	kfree(drvdata);
> +	return ret;
> +}
> +
> +static int arm_trbe_device_remove(struct platform_device *pdev)
> +{
> +	struct coresight_platform_data *pdata = dev_get_platdata(&pdev->dev);
> +	struct trbe_drvdata *drvdata = platform_get_drvdata(pdev);
> +
> +	arm_trbe_remove_coresight(drvdata);
> +	arm_trbe_remove_cpuhp(drvdata);

Shouldn't this be called before arm_trbe_remove_coresight()?

> +	arm_trbe_remove_irq(drvdata);
> +	kfree(pdata);
> +	kfree(drvdata);
> +	return 0;
> +}
> +
> +static const struct of_device_id arm_trbe_of_match[] = {
> +	{ .compatible = "arm,trace-buffer-extension"},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, arm_trbe_of_match);
> +
> +static struct platform_driver arm_trbe_driver = {
> +	.driver	= {
> +		.name = DRVNAME,
> +		.of_match_table = of_match_ptr(arm_trbe_of_match),
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe	= arm_trbe_device_probe,
> +	.remove	= arm_trbe_device_remove,
> +};
> +
> +static int __init arm_trbe_init(void)
> +{
> +	int ret;
> +
> +	if (arm64_kernel_unmapped_at_el0()) {
> +		pr_err("TRBE wouldn't work if kernel gets unmapped at EL0\n");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	ret = platform_driver_register(&arm_trbe_driver);
> +	if (!ret)
> +		return 0;
> +
> +	pr_err("Error registering %s platform driver\n", DRVNAME);
> +	return ret;
> +}
> +
> +static void __exit arm_trbe_exit(void)
> +{
> +	platform_driver_unregister(&arm_trbe_driver);
> +}
> +module_init(arm_trbe_init);
> +module_exit(arm_trbe_exit);
> +
> +MODULE_AUTHOR("Anshuman Khandual <anshuman.khandual@arm.com>");
> +MODULE_DESCRIPTION("Arm Trace Buffer Extension (TRBE) driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/hwtracing/coresight/coresight-trbe.h b/drivers/hwtracing/coresight/coresight-trbe.h
> new file mode 100644
> index 0000000..43308bc
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-trbe.h
> @@ -0,0 +1,160 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * This contains all required hardware related helper functions for
> + * Trace Buffer Extension (TRBE) driver in the coresight framework.
> + *
> + * Copyright (C) 2020 ARM Ltd.
> + *
> + * Author: Anshuman Khandual <anshuman.khandual@arm.com>
> + */
> +#include <linux/coresight.h>
> +#include <linux/device.h>
> +#include <linux/irq.h>
> +#include <linux/kernel.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/smp.h>
> +
> +#include "coresight-etm-perf.h"
> +
> +DECLARE_PER_CPU(struct coresight_device *, csdev_sink);
> +
> +static inline bool is_trbe_available(void)
> +{
> +	u64 aa64dfr0 = read_sysreg_s(SYS_ID_AA64DFR0_EL1);
> +	unsigned int trbe = cpuid_feature_extract_unsigned_field(aa64dfr0, ID_AA64DFR0_TRBE_SHIFT);
> +
> +	return trbe >= 0b0001;
> +}
> +
> +static inline bool is_trbe_enabled(void)
> +{
> +	u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);
> +
> +	return trblimitr & TRBLIMITR_ENABLE;
> +}
> +
> +#define TRBE_EC_OTHERS		0
> +#define TRBE_EC_STAGE1_ABORT	36
> +#define TRBE_EC_STAGE2_ABORT	37
> +
> +static inline int get_trbe_ec(u64 trbsr)
> +{
> +	return (trbsr >> TRBSR_EC_SHIFT) & TRBSR_EC_MASK;
> +}
> +
> +#define TRBE_BSC_NOT_STOPPED	0
> +#define	TRBE_BSC_FILLED		1
> +#define TRBE_BSC_TRIGGERED	2
> +
> +static inline int get_trbe_bsc(u64 trbsr)
> +{
> +	return (trbsr >> TRBSR_BSC_SHIFT) & TRBSR_BSC_MASK;
> +}
> +
> +static inline void clr_trbe_irq(void)
> +{
> +	u64 trbsr = read_sysreg_s(SYS_TRBSR_EL1);
> +
> +	trbsr &= ~TRBSR_IRQ;
> +	write_sysreg_s(trbsr, SYS_TRBSR_EL1);
> +}
> +
> +static inline bool is_trbe_irq(u64 trbsr)
> +{
> +	return trbsr & TRBSR_IRQ;
> +}
> +
> +static inline bool is_trbe_trg(u64 trbsr)
> +{
> +	return trbsr & TRBSR_TRG;
> +}
> +
> +static inline bool is_trbe_wrap(u64 trbsr)
> +{
> +	return trbsr & TRBSR_WRAP;
> +}
> +
> +static inline bool is_trbe_abort(u64 trbsr)
> +{
> +	return trbsr & TRBSR_ABORT;
> +}
> +
> +static inline bool is_trbe_running(u64 trbsr)
> +{
> +	return !(trbsr & TRBSR_STOP);
> +}
> +
> +#define TRBE_TRIG_MODE_STOP		0
> +#define TRBE_TRIG_MODE_IRQ		1
> +#define TRBE_TRIG_MODE_IGNORE		3
> +
> +#define TRBE_FILL_MODE_FILL		0
> +#define TRBE_FILL_MODE_WRAP		1
> +#define TRBE_FILL_MODE_CIRCULAR_BUFFER	3
> +
> +static inline void set_trbe_disabled(void)
> +{
> +	u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);
> +
> +	trblimitr &= ~TRBLIMITR_ENABLE;
> +	write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);
> +}
> +
> +static inline bool get_trbe_flag_update(u64 trbidr)
> +{
> +	return trbidr & TRBIDR_FLAG;
> +}
> +
> +static inline bool is_trbe_programmable(u64 trbidr)
> +{
> +	return !(trbidr & TRBIDR_PROG);
> +}
> +
> +static inline int get_trbe_address_align(u64 trbidr)
> +{
> +	return (trbidr >> TRBIDR_ALIGN_SHIFT) & TRBIDR_ALIGN_MASK;
> +}
> +
> +static inline unsigned long get_trbe_write_pointer(void)
> +{
> +	u64 trbptr = read_sysreg_s(SYS_TRBPTR_EL1);
> +	unsigned long addr = (trbptr >> TRBPTR_PTR_SHIFT) & TRBPTR_PTR_MASK;
> +
> +	return addr;
> +}
> +
> +static inline void set_trbe_write_pointer(unsigned long addr)
> +{
> +	WARN_ON(is_trbe_enabled());
> +	addr = (addr >> TRBPTR_PTR_SHIFT) & TRBPTR_PTR_MASK;
> +	write_sysreg_s(addr, SYS_TRBPTR_EL1);
> +}
> +
> +static inline unsigned long get_trbe_limit_pointer(void)
> +{
> +	u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);
> +	unsigned long limit = (trblimitr >> TRBLIMITR_LIMIT_SHIFT) & TRBLIMITR_LIMIT_MASK;
> +	unsigned long addr = limit << TRBLIMITR_LIMIT_SHIFT;
> +
> +	WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));
> +	return addr;
> +}
> +
> +static inline unsigned long get_trbe_base_pointer(void)
> +{
> +	u64 trbbaser = read_sysreg_s(SYS_TRBBASER_EL1);
> +	unsigned long addr = (trbbaser >> TRBBASER_BASE_SHIFT) & TRBBASER_BASE_MASK;
> +
> +	addr = addr << TRBBASER_BASE_SHIFT;
> +	WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));
> +	return addr;
> +}
> +
> +static inline void set_trbe_base_pointer(unsigned long addr)
> +{
> +	WARN_ON(is_trbe_enabled());
> +	WARN_ON(!IS_ALIGNED(addr, (1UL << TRBLIMITR_LIMIT_SHIFT)));
> +	WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));
> +	write_sysreg_s(addr, SYS_TRBBASER_EL1);
> +}
> -- 
> 2.7.4
>