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Subject: Re: [PATCH V3 11/14] coresight: sink: Add TRBE driver
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
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
References: <1611737738-1493-1-git-send-email-anshuman.khandual@arm.com>
 <1611737738-1493-12-git-send-email-anshuman.khandual@arm.com>
 <20210211190024.GD2186000@xps15>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <be83fd32-e552-ac06-6ee5-3bf22c6daab2@arm.com>
Date:   Fri, 12 Feb 2021 09:01:37 +0530
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On 2/12/21 12:30 AM, Mathieu Poirier wrote:
> 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.

I guess it should be "no room left" instead of "not much room left". If there
is only a single page and the buffer is partially filled, there wont be space
left to write the traces after the WRITE/LIMIT pointer's PAGE_SIZE alignment.

        /*
         * TRBE LIMIT and TRBE WRITE pointers must be page aligned. But with
         * just a single page, there would not be any room left while writing
         * into a partially filled TRBE buffer after the page size alignment.
         * Hence restrict the minimum buffer size as two pages.
         */

> 
> 
>> +	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

There are many arithmetic and comparison operations involving trbe_base
element. Hence it might be better to keep it as unsigned long, also to
keeps it consistent with other pointers i.e trbe_write, trbe_limit.

Snippet from $cat drivers/hwtracing/coresight/coresight-trbe.c | grep "trbe_base"
There are just two places type casting trbe_base back to (void *).

	memset((void *)buf->trbe_base + head, ETE_IGNORE_PACKET, len);
	return buf->trbe_base + offset;
	WARN_ON(buf->trbe_write < buf->trbe_base);
	set_trbe_base_pointer(buf->trbe_base);
	buf->trbe_base = (unsigned long)vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL);
	if (IS_ERR((void *)buf->trbe_base)) {
		return ERR_PTR(buf->trbe_base);
	buf->trbe_limit = buf->trbe_base + nr_pages * PAGE_SIZE;
	buf->trbe_write = buf->trbe_base;
	vunmap((void *)buf->trbe_base);
	base = get_trbe_base_pointer();
	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
	if (buf->trbe_limit == buf->trbe_base) {
	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
	if (buf->trbe_limit == buf->trbe_base) {
	offset = get_trbe_limit_pointer() - get_trbe_base_pointer();
	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
	if (buf->trbe_limit == buf->trbe_base) {
	WARN_ON(buf->trbe_base != get_trbe_base_pointer());
		if (get_trbe_write_pointer() == get_trbe_base_pointer())
  
> casting?  And IS_ERR() doesn't work with vmap().

Sure, will drop IS_ERR() here.


> 
>> +		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.

I made it up to refer TRBIDR_EL1.F as "Dirty (and Access Flag) Bit Management".
Could change it as "afdbm" to be more specific or if it is preferred.

> 
>> +
>> +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

Sure, will do.

> 
>         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 

Okay, will return trbe_online here.

> 
>> +
>> +	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().

Okay, will do the following change.

--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -916,15 +916,18 @@ static int arm_trbe_cpu_teardown(unsigned int cpu, struct hlist_node *node)
 static int arm_trbe_probe_cpuhp(struct trbe_drvdata *drvdata)
 {
        enum cpuhp_state trbe_online;
+       int ret;
 
        trbe_online = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, DRVNAME,
                                              arm_trbe_cpu_startup, arm_trbe_cpu_teardown);
        if (trbe_online < 0)
                return trbe_online;
 
-       if (cpuhp_state_add_instance(trbe_online, &drvdata->hotplug_node))
-               return -EINVAL;
-
+       ret = cpuhp_state_add_instance(trbe_online, &drvdata->hotplug_node);
+       if (ret) {
+               cpuhp_remove_multi_state(trbe_online);
+               return ret;
+       }
        drvdata->trbe_online = trbe_online;
        return 0;
 }

> 
> 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()?

Yes, will change the order.

- Anshuman