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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>
 <20210205175330.GB1636242@xps15> <20210209173913.GA2186000@xps15>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <e5eff56e-d894-447f-2b49-b1f2a8967ed5@arm.com>
Date:   Wed, 10 Feb 2021 09:42:29 +0530
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On 2/9/21 11:09 PM, Mathieu Poirier wrote:
> On Fri, Feb 05, 2021 at 10:53:30AM -0700, 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.
>>>
>>
>> I got this message when applying the patch: 
>>
>> Applying: coresight: sink: Add TRBE driver
>> .git/rebase-apply/patch:76: new blank line at EOF.
>> +
>> warning: 1 line adds whitespace errors.
>>  
>>> 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
>>> +
>>
>> Please add documentation for these, the same way it was done for all the other CS
>> components [1].
>>
>> [1]. https://elixir.bootlin.com/linux/latest/source/Documentation/ABI/testing
>> (sysfs-bus-coresight-device-xyz)
>>
>>> 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"
>>
>> Shouldn't that be "tristate"?
>>
>>> +	depends on ARM64
>>
>> I would make it dependent on ETMv4 as well since it can only be used by that
>> component.
>>
>>> +	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.
>>
>> Please add:
>>
>>           "To compile this driver as a module, choose M here: the
>>           module will be called coresight-trbe."
>>
>> I'm out of time for today, I will continue on Monday.
>>
>> Mathieu
>>
>>> +
>>>  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.
>>> +	 */
>>> +	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)) {
>>> +		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();
> 
> There is a comment in the SPE driver about this.  Since this driver closely
> follows that implementation it would be nice to have the comments as well.
> Otherwise the reader has to constantly go back to the original driver.

Sure, will add the following comment before irq_work_run().

        /*
         * Ensure perf callbacks have completed, which may disable the
         * profiling buffer in response to a TRUNCATION flag.
         */

> 
> I will come back to this function later.

Okay.

> 
>>> +
>>> +	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);
>>> +
>>> +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;
> 
> Where was the memory for cpudata allocated?  As far as I can tell, at this time
> it is just a pointer that was not allocated and as such it should be NULL.

cpudata gets allocated in arm_trbe_probe_coresight() just before calling
individual CPU based probes i.e arm_trbe_probe_coresight_cpu() directly
and via smp_call_function_many().

arm_trbe_device_probe()
	arm_trbe_probe_coresight()
		arm_trbe_probe_coresight_cpu()

> 
>>> +
>>> +	if (trbe_csdev)
>>> +		return;
>>> +
>>> +	cpudata->cpu = smp_processor_id();
> 
> Why call this again when you already did above?  And how is

Right, this is redundant. Will just assign it as cpu which has already
been computed.

> arm_trbe_probe_coresight_cpu() is called for every CPU in the system?

During boot in arm_trbe_probe_coresight(), it is called once directly on
the executing cpu and on all other via smp_call_function_many().

> 
>>> +	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);
>>> +	if (trbe_online < 0)
>>> +		return -EINVAL;
>>> +
>>> +	if (cpuhp_state_add_instance(trbe_online, &drvdata->hotplug_node))
>>> +		return -EINVAL;
>>> +
>>> +	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) {
> 
> Please use function platform_get_irq() properly - there is even an example on
> how to do so in the documentation section of the function.

The documentation says, the format should be.

int irq = platform_get_irq(pdev, 0);
if (irq < 0)
	return irq;

Will change the conditional check above.

> 
>>> +		pr_err("IRQ not found for the platform device\n");
>>> +		return -ENXIO;
> 
> Why use a different error code?

We could return the irq (which is < 0) but followed the SPE
driver which returns ENXIO here. Happy to change either way.

> 
>>> +	}
>>> +
>>> +	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;
> 
> Here too you need to use the error code from the calling function rather than
> making your own.  Please revise for the entire patch.

Okay, will capture the return value from request_percpu_irq() and
return the same when it is an error case i.e being positive.

> 
>>> +	}
>>> +	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;
> 
>         if (!drvdata)

Changed.

> 
>>> +
>>> +	pdata = coresight_get_platform_data(dev);
>>> +	if (IS_ERR(pdata)) {
>>> +		kfree(drvdata);
> 
> No need to do this since devm_kzalloc() was used above.

Suzuki had pointed out these issues, have already incorporated them i.e
dropped kfree() here.

> 
>>> +		return -ENOMEM;
> 
> Why not using the error from coresight_get_platform_data() instead of
> masking it?

Okay, will return PTR_ERR(pdata) instead.

> 
>>> +	}
>>> +
>>> +	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);
> 
> Same here - both @pdata and @drvdata have been allocated by devm_kzalloc().
> devm_kzalloc().

Dropped these kfree() statements.

- Anshuman