[PATCH v4 18/19] coresight: sink: Add TRBE driver

From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, mathieu.poirier@linaro.org,
	mike.leach@linaro.org, anshuman.khandual@arm.com,
	leo.yan@linaro.org, Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: [PATCH v4 18/19] coresight: sink: Add TRBE driver
Date: Thu, 25 Feb 2021 19:35:42 +0000	[thread overview]
Message-ID: <20210225193543.2920532-19-suzuki.poulose@arm.com> (raw)
In-Reply-To: <20210225193543.2920532-1-suzuki.poulose@arm.com>

From: Anshuman Khandual <anshuman.khandual@arm.com>

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>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Changes:
 - Replaced TRBLIMITR_LIMIT_SHIFT with TRBBASER_BASE_SHIFT in set_trbe_base_pointer()
 - Dropped TRBBASER_BASE_MASK and TRBBASER_BASE_SHIFT from get_trbe_base_pointer()
 - Indentation changes for TRBE_BSC_NOT_[STOPPED|FILLED|TRIGGERED] definitions
 - Moved DECLARE_PER_CPU(...., csdev_sink) into coresight-priv.h
 - Moved isb() from trbe_enable_hw() into set_trbe_limit_pointer_enabled()
 - Dropped the space after type casting before vmap()
 - Return 0 instead of EINVAL in arm_trbe_update_buffer()
 - Add a comment in trbe_handle_overflow()
 - Add a comment in arm_trbe_cpu_startup()
 - Unregister coresight TRBE device when not supported
 - Fix potential NULL handle dereference in IRQ handler with a spurious IRQ
 - Read TRBIDR after is_trbe_programmable() in arm_trbe_probe_coresight_cpu()
 - Replaced and modified trbe_drain_and_disable_local() in IRQ handler
 - Updated arm_trbe_update_buffer() for handling a missing interrupt
 - Dropped kfree() for all devm_xxx() allocated buffer
 - Dropped additional blank line in documentation coresight/coresight-trbe.rst
 - Added Documentation/ABI/testing/sysfs-bus-coresight-devices-trbe
 - Changed CONFIG_CORESIGHT_TRBE options, dependencies and helper write up
 - Added comment for irq_work_run()
 - Updated comment for minumum buffer length in arm_trbe_alloc_buffer()
 - Dropped redundant smp_processor_id() from arm_trbe_probe_coresight_cpu()
 - Fixed indentation in arm_trbe_probe_cpuhp()
 - Added static for arm_trbe_free_buffer()
 - Added comment for trbe_base element in trbe_buf structure
 - Dropped IS_ERR() check from vmap() returned pointer
 - Added WARN_ON(trbe_csdev) in arm_trbe_probe_coresight_cpu()
 - Changed TRBE device names from arm_trbeX to just trbeX
 - Dropped unused argument perf_output_handle from trbe_get_fault_act()
 - Dropped IS_ERR() from kzalloc_node()/kcalloc() buffer in arm_trbe_alloc_buffer()
 - Dropped IS_ERR() and return -ENOMEM in arm_trbe_probe_coresight()
 - Moved TRBE HW disabling before coresight cleanup in arm_trbe_remove_coresight_cpu()
 - Changed error return codes from arm_trbe_probe_irq()
 - Changed error return codes from arm_trbe_device_probe()
 - Changed arm_trbe_remove_coresight() order in arm_trbe_device_remove()
 - Changed TRBE CPU support probe/remove sequence with for_each_cpu() iterator
 - Changed coresight_register() in arm_trbe_probe_coresight_cpu()
 - Changed error return code when cpuhp_setup_state_multi() fails in arm_trbe_probe_cpuhp()
 - Changed error return code when cpuhp_state_add_instance() fails in arm_trbe_probe_cpuhp()
 - Changed trbe_dbm as trbe_flag including its sysfs interface
 - Handle race between update_buffer & IRQ handler
 - Rework and split the TRBE probe to avoid lockdep due to memory allocation
   from IPI calls (via coresight_register())
 - Fix handle->head updat for snapshot mode.
---
 .../testing/sysfs-bus-coresight-devices-trbe  |   14 +
 .../trace/coresight/coresight-trbe.rst        |   38 +
 drivers/hwtracing/coresight/Kconfig           |   14 +
 drivers/hwtracing/coresight/Makefile          |    1 +
 drivers/hwtracing/coresight/coresight-trbe.c  | 1149 +++++++++++++++++
 drivers/hwtracing/coresight/coresight-trbe.h  |  153 +++
 6 files changed, 1369 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-coresight-devices-trbe
 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/ABI/testing/sysfs-bus-coresight-devices-trbe b/Documentation/ABI/testing/sysfs-bus-coresight-devices-trbe
new file mode 100644
index 000000000000..ad3bbc6fa751
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-trbe
@@ -0,0 +1,14 @@
+What:		/sys/bus/coresight/devices/trbe<cpu>/align
+Date:		March 2021
+KernelVersion:	5.13
+Contact:	Anshuman Khandual <anshuman.khandual@arm.com>
+Description:	(Read) Shows the TRBE write pointer alignment. This value
+		is fetched from the TRBIDR register.
+
+What:		/sys/bus/coresight/devices/trbe<cpu>/flag
+Date:		March 2021
+KernelVersion:	5.13
+Contact:	Anshuman Khandual <anshuman.khandual@arm.com>
+Description:	(Read) Shows if TRBE updates in the memory are with access
+		and dirty flag updates as well. This value is fetched from
+		the TRBIDR register.
diff --git a/Documentation/trace/coresight/coresight-trbe.rst b/Documentation/trace/coresight/coresight-trbe.rst
new file mode 100644
index 000000000000..b9928ef148da
--- /dev/null
+++ b/Documentation/trace/coresight/coresight-trbe.rst
@@ -0,0 +1,38 @@
+.. 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
+generators (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 flag
+
+*Key file items are:-*
+   * ``align``: TRBE write pointer alignment
+   * ``flag``: TRBE updates memory with access and dirty flags
diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
index f154ae7e705d..84530fd80998 100644
--- a/drivers/hwtracing/coresight/Kconfig
+++ b/drivers/hwtracing/coresight/Kconfig
@@ -173,4 +173,18 @@ config CORESIGHT_CTI_INTEGRATION_REGS
 	  CTI trigger connections between this and other devices.These
 	  registers are not used in normal operation and can leave devices in
 	  an inconsistent state.
+
+config CORESIGHT_TRBE
+	tristate "Trace Buffer Extension (TRBE) driver"
+	depends on ARM64 && CORESIGHT_SOURCE_ETM4X
+	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.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called coresight-trbe.
 endif
diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
index f20e357758d1..d60816509755 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 000000000000..41a012b525bb
--- /dev/null
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -0,0 +1,1149 @@
+// 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 <asm/barrier.h>
+#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 {
+	/*
+	 * Even though trbe_base represents vmap()
+	 * mapped allocated buffer's start address,
+	 * it's being as unsigned long for various
+	 * arithmetic and comparision operations &
+	 * also to be consistent with trbe_write &
+	 * trbe_limit sibling pointers.
+	 */
+	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_flag;
+	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)
+{
+	tsb_csync();
+	dsb(nsh);
+}
+
+static void trbe_drain_and_disable_local(void)
+{
+	u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);
+
+	trbe_drain_buffer();
+
+	/*
+	 * Disable the TRBE without clearing LIMITPTR which
+	 * might be required for fetching the buffer limits.
+	 */
+	trblimitr &= ~TRBLIMITR_ENABLE;
+	write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);
+	isb();
+}
+
+static void trbe_reset_local(void)
+{
+	trbe_drain_and_disable_local();
+	write_sysreg_s(0, SYS_TRBLIMITR_EL1);
+	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);
+
+	/* Synchronize the TRBE enable event */
+	isb();
+}
+
+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);
+}
+
+static enum trbe_fault_action trbe_get_fault_act(u64 trbsr)
+{
+	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 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 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 (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	pglist = kcalloc(nr_pages, sizeof(*pglist), GFP_KERNEL);
+	if (!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 (!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;
+}
+
+static 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;
+	enum trbe_fault_action act;
+	unsigned long size, offset;
+	unsigned long write, base, status;
+	unsigned long flags;
+
+	WARN_ON(buf->cpudata != cpudata);
+	WARN_ON(cpudata->cpu != smp_processor_id());
+	WARN_ON(cpudata->drvdata != drvdata);
+	if (cpudata->mode != CS_MODE_PERF)
+		return 0;
+
+	perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW);
+
+	/*
+	 * We are about to disable the TRBE. And this could in turn
+	 * fill up the buffer triggering, an IRQ. This could be consumed
+	 * by the PE asynchronously, causing a race here against
+	 * the IRQ handler in closing out the handle. So, let us
+	 * make sure the IRQ can't trigger while we are collecting
+	 * the buffer. We also make sure that a WRAP event is handled
+	 * accordingly.
+	 */
+	local_irq_save(flags);
+
+	/*
+	 * 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()) {
+		size = 0;
+		goto done;
+	}
+	/*
+	 * 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();
+	write = get_trbe_write_pointer();
+	base = get_trbe_base_pointer();
+
+	/* Check if there is a pending interrupt and handle it here */
+	status = read_sysreg_s(SYS_TRBSR_EL1);
+	if (is_trbe_irq(status)) {
+
+		/*
+		 * Now that we are handling the IRQ here, clear the IRQ
+		 * from the status, to let the irq handler know that it
+		 * is taken care of.
+		 */
+		clr_trbe_irq();
+		isb();
+
+		act = trbe_get_fault_act(status);
+		/*
+		 * If this was not due to a WRAP event, we have some
+		 * errors and as such buffer is empty.
+		 */
+		if (act != TRBE_FAULT_ACT_WRAP) {
+			size = 0;
+			goto done;
+		}
+
+		/*
+		 * Otherwise, the buffer is full and the write pointer
+		 * has reached base. Adjust this back to the Limit pointer
+		 * for correct size.
+		 */
+		write = get_trbe_limit_pointer();
+	}
+
+	offset = write - base;
+	if (WARN_ON_ONCE(offset < PERF_IDX2OFF(handle->head, buf)))
+		size = 0;
+	else
+		size = offset - PERF_IDX2OFF(handle->head, buf);
+
+done:
+	local_irq_restore(flags);
+
+	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 += size;
+
+	perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW);
+	perf_aux_output_end(handle, size);
+	event_data = perf_aux_output_begin(handle, event);
+	if (!event_data) {
+		/*
+		 * We are unable to restart the trace collection,
+		 * thus leave the TRBE disabled. The etm-perf driver
+		 * is able to detect this with a disconnected handle
+		 * (handle->event = NULL).
+		 */
+		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 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;
+	u64 status;
+
+	/*
+	 * Ensure the trace is visible to the CPUs and
+	 * any external aborts have been resolved.
+	 */
+	trbe_drain_and_disable_local();
+
+	status = read_sysreg_s(SYS_TRBSR_EL1);
+	/*
+	 * If the pending IRQ was handled by update_buffer callback
+	 * we have nothing to do here.
+	 */
+	if (!is_trbe_irq(status))
+		return IRQ_NONE;
+
+	clr_trbe_irq();
+	isb();
+
+	if (WARN_ON_ONCE(!handle) || !perf_get_aux(handle))
+		return IRQ_NONE;
+
+	if (!is_perf_trbe(handle))
+		return IRQ_NONE;
+
+	/*
+	 * Ensure perf callbacks have completed, which may disable
+	 * the trace buffer in response to a TRUNCATION flag.
+	 */
+	irq_work_run();
+
+	act = trbe_get_fault_act(status);
+	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 flag_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_flag);
+}
+static DEVICE_ATTR_RO(flag);
+
+static struct attribute *arm_trbe_attrs[] = {
+	&dev_attr_align.attr,
+	&dev_attr_flag.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_enable_cpu(void *info)
+{
+	struct trbe_drvdata *drvdata = info;
+
+	trbe_reset_local();
+	enable_percpu_irq(drvdata->irq, IRQ_TYPE_NONE);
+}
+
+static void arm_trbe_register_coresight_cpu(struct trbe_drvdata *drvdata, int cpu)
+{
+	struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
+	struct coresight_device *trbe_csdev = coresight_get_percpu_sink(cpu);
+	struct coresight_desc desc = { 0 };
+	struct device *dev;
+
+	if (WARN_ON(trbe_csdev))
+		return;
+
+	dev = &cpudata->drvdata->pdev->dev;
+	desc.name = devm_kasprintf(dev, GFP_KERNEL, "trbe%d", cpu);
+	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);
+	coresight_set_percpu_sink(cpu, trbe_csdev);
+	return;
+cpu_clear:
+	cpumask_clear_cpu(cpu, &drvdata->supported_cpus);
+}
+
+static void arm_trbe_probe_cpu(void *info)
+{
+	struct trbe_drvdata *drvdata = info;
+	int cpu = smp_processor_id();
+	struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
+	u64 trbidr;
+
+	if (WARN_ON(!cpudata))
+		goto cpu_clear;
+
+	if (!is_trbe_available()) {
+		pr_err("TRBE is not implemented on cpu %d\n", cpu);
+		goto cpu_clear;
+	}
+
+	trbidr = read_sysreg_s(SYS_TRBIDR_EL1);
+	if (!is_trbe_programmable(trbidr)) {
+		pr_err("TRBE is owned in higher exception level on cpu %d\n", cpu);
+		goto cpu_clear;
+	}
+
+	cpudata->trbe_align = 1ULL << get_trbe_address_align(trbidr);
+	if (cpudata->trbe_align > SZ_2K) {
+		pr_err("Unsupported alignment on cpu %d\n", cpu);
+		goto cpu_clear;
+	}
+	cpudata->trbe_flag = get_trbe_flag_update(trbidr);
+	cpudata->cpu = cpu;
+	cpudata->drvdata = drvdata;
+	return;
+cpu_clear:
+	cpumask_clear_cpu(cpu, &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 = coresight_get_percpu_sink(cpu);
+
+	disable_percpu_irq(drvdata->irq);
+	trbe_reset_local();
+	if (trbe_csdev) {
+		coresight_unregister(trbe_csdev);
+		cpudata->drvdata = NULL;
+		coresight_set_percpu_sink(cpu, NULL);
+	}
+}
+
+static int arm_trbe_probe_coresight(struct trbe_drvdata *drvdata)
+{
+	int cpu;
+
+	drvdata->cpudata = alloc_percpu(typeof(*drvdata->cpudata));
+	if (!drvdata->cpudata)
+		return -ENOMEM;
+
+	for_each_cpu(cpu, &drvdata->supported_cpus) {
+		smp_call_function_single(cpu, arm_trbe_probe_cpu, drvdata, 1);
+		if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
+			arm_trbe_register_coresight_cpu(drvdata, cpu);
+		if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
+			smp_call_function_single(cpu, arm_trbe_enable_cpu, drvdata, 1);
+	}
+	return 0;
+}
+
+static int arm_trbe_remove_coresight(struct trbe_drvdata *drvdata)
+{
+	int cpu;
+
+	for_each_cpu(cpu, &drvdata->supported_cpus)
+		smp_call_function_single(cpu, 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 this CPU was not probed for TRBE,
+		 * initialize it now.
+		 */
+		if (!coresight_get_percpu_sink(cpu)) {
+			arm_trbe_probe_cpu(drvdata);
+			if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
+				arm_trbe_register_coresight_cpu(drvdata, cpu);
+			if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
+				arm_trbe_enable_cpu(drvdata);
+		} else {
+			arm_trbe_enable_cpu(drvdata);
+		}
+	}
+	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;
+	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;
+
+	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;
+}
+
+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)
+{
+	int ret;
+
+	drvdata->irq = platform_get_irq(pdev, 0);
+	if (drvdata->irq < 0) {
+		pr_err("IRQ not found for the platform device\n");
+		return drvdata->irq;
+	}
+
+	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;
+
+	ret = request_percpu_irq(drvdata->irq, arm_trbe_irq_handler, DRVNAME, drvdata->handle);
+	if (ret) {
+		free_percpu(drvdata->handle);
+		return ret;
+	}
+	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 (!drvdata)
+		return -ENOMEM;
+
+	pdata = coresight_get_platform_data(dev);
+	if (IS_ERR(pdata))
+		return PTR_ERR(pdata);
+
+	dev_set_drvdata(dev, drvdata);
+	dev->platform_data = pdata;
+	drvdata->pdev = pdev;
+	ret = arm_trbe_probe_irq(pdev, drvdata);
+	if (ret)
+		return ret;
+
+	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);
+	return ret;
+}
+
+static int arm_trbe_device_remove(struct platform_device *pdev)
+{
+	struct trbe_drvdata *drvdata = platform_get_drvdata(pdev);
+
+	arm_trbe_remove_cpuhp(drvdata);
+	arm_trbe_remove_coresight(drvdata);
+	arm_trbe_remove_irq(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 000000000000..499b846ccfee
--- /dev/null
+++ b/drivers/hwtracing/coresight/coresight-trbe.h
@@ -0,0 +1,153 @@
+/* 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"
+
+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)
+{
+	return read_sysreg_s(SYS_TRBPTR_EL1);
+}
+
+static inline void set_trbe_write_pointer(unsigned long addr)
+{
+	WARN_ON(is_trbe_enabled());
+	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_MASK << 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 << TRBBASER_BASE_SHIFT)));
+	WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));
+	write_sysreg_s(addr, SYS_TRBBASER_EL1);
+}
-- 
2.24.1

