Re: [PATCH V3 11/14] coresight: sink: Add TRBE driver

Suzuki K Poulose
2021-01-29T10:25:06Z

Hi Anshuman

On 1/27/21 8:55 AM, 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>

This version looks functionally correct to me. There are some minor
issues with the devm_ allocated memory and some driver hardening comments.
I ran this on a model and have tested this with various scenarios.

> ---
> 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);
Personally, I prefer the isb() here rather than at the caller site, to make sure
it is all contained here and more importantly we don't execute any other instruction
before the "isb()" as the tracing may be enabled for the kernel.

> +}
> +
> +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);

minor nit: space after casting.

> + 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;

Please return 0 here. As we are expected to pass an "unsigned" size.

> +
> + /*
> + * 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);

It may be a good idea to verify that the size computation here doesn't overflow.
e.g broken interrupt could potentially leave us with "write == base". I understand
this is a hardware issue, but the software can be resilient to not send bogus
results.

> + 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) {

We may add a comment here to explain how this would be handled ? e.g,

/*
* We are unable to restart the trace collection,
* thus leave the TRBE disabled. The etm-perf driver
* is able to detect this with a disconnnected 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 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))

We may want to ensure that handle is not NULL, which can only happen if the
hardware is not following the software.

if (WARN_ON_ONCE(!handle) || !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);
> +
> +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);

This must be done only after the "is_trbe_available()". Otherwise
we get an UNDEFINED instruction abort.

> + 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;

Should we unregister the coresight device in this case ? There is no point
in having the device around if it is not supported.

> + }
> + 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);
> +

nit: Is it better to use this_cpu_ptr() every where above/below to make it explicit ?

> + 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)) {

nit: Add a comment ?

/*
* If this CPU was not probed for TRBE, initialize
* it now.
*/

> + 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) {
> + 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);

Not sure if this is necessary. We don't have any CoreSight specific
data in the bindings.

> + if (IS_ERR(pdata)) {
> + kfree(drvdata);

This is not required. The cleanup should automatically free this up.
In fact this will be problematic and will cause double free.

> + 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);

None of these "kfree" is needed. It will be automatically freed
when the probe fails.

> + 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);
> + arm_trbe_remove_irq(drvdata);

> + kfree(pdata);
> + kfree(drvdata);

Same as above.

> + return 0;
> +}
> +
> +static const struct of_device_id arm_trbe_of_match[] = {
> + { .compatible = "arm,trace-buffer-extension"},
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, arm_trbe_of_match);
> +
> +static struct platform_driver arm_trbe_driver = {
> + .driver = {
> + .name = DRVNAME,
> + .of_match_table = of_match_ptr(arm_trbe_of_match),
> + .suppress_bind_attrs = true,
> + },
> + .probe = arm_trbe_device_probe,
> + .remove = arm_trbe_device_remove,
> +};
> +
> +static int __init arm_trbe_init(void)
> +{
> + int ret;
> +
> + if (arm64_kernel_unmapped_at_el0()) {
> + pr_err("TRBE wouldn't work if kernel gets unmapped at EL0\n");
> + return -EOPNOTSUPP;
> + }
> +
> + ret = platform_driver_register(&arm_trbe_driver);
> + if (!ret)
> + return 0;
> +
> + pr_err("Error registering %s platform driver\n", DRVNAME);
> + return ret;
> +}
> +
> +static void __exit arm_trbe_exit(void)
> +{
> + platform_driver_unregister(&arm_trbe_driver);
> +}
> +module_init(arm_trbe_init);
> +module_exit(arm_trbe_exit);
> +
> +MODULE_AUTHOR("Anshuman Khandual <anshuman.khandual@arm.com>");
> +MODULE_DESCRIPTION("Arm Trace Buffer Extension (TRBE) driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/hwtracing/coresight/coresight-trbe.h b/drivers/hwtracing/coresight/coresight-trbe.h
> new file mode 100644
> index 0000000..43308bc
> --- /dev/null
> +++ b/drivers/hwtracing/coresight/coresight-trbe.h
> @@ -0,0 +1,160 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * This contains all required hardware related helper functions for
> + * Trace Buffer Extension (TRBE) driver in the coresight framework.
> + *
> + * Copyright (C) 2020 ARM Ltd.
> + *
> + * Author: Anshuman Khandual <anshuman.khandual@arm.com>
> + */
> +#include <linux/coresight.h>
> +#include <linux/device.h>
> +#include <linux/irq.h>
> +#include <linux/kernel.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/smp.h>
> +
> +#include "coresight-etm-perf.h"
> +
> +DECLARE_PER_CPU(struct coresight_device *, csdev_sink);

This belongs to coresight-priv.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

nit: Use space instead of TAB here.

> +#define TRBE_BSC_TRIGGERED 2
> +
> +static inline int get_trbe_bsc(u64 trbsr)
> +{
> + return (trbsr >> TRBSR_BSC_SHIFT) & TRBSR_BSC_MASK;
> +}
> +
> +static inline void clr_trbe_irq(void)
> +{
> + u64 trbsr = read_sysreg_s(SYS_TRBSR_EL1);
> +
> + trbsr &= ~TRBSR_IRQ;
> + write_sysreg_s(trbsr, SYS_TRBSR_EL1);
> +}
> +
> +static inline bool is_trbe_irq(u64 trbsr)
> +{
> + return trbsr & TRBSR_IRQ;
> +}
> +
> +static inline bool is_trbe_trg(u64 trbsr)
> +{
> + return trbsr & TRBSR_TRG;
> +}
> +
> +static inline bool is_trbe_wrap(u64 trbsr)
> +{
> + return trbsr & TRBSR_WRAP;
> +}
> +
> +static inline bool is_trbe_abort(u64 trbsr)
> +{
> + return trbsr & TRBSR_ABORT;
> +}
> +
> +static inline bool is_trbe_running(u64 trbsr)
> +{
> + return !(trbsr & TRBSR_STOP);
> +}
> +
> +#define TRBE_TRIG_MODE_STOP 0
> +#define TRBE_TRIG_MODE_IRQ 1
> +#define TRBE_TRIG_MODE_IGNORE 3
> +
> +#define TRBE_FILL_MODE_FILL 0
> +#define TRBE_FILL_MODE_WRAP 1
> +#define TRBE_FILL_MODE_CIRCULAR_BUFFER 3
> +
> +static inline void set_trbe_disabled(void)
> +{
> + u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);
> +
> + trblimitr &= ~TRBLIMITR_ENABLE;
> + write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);
> +}
> +
> +static inline bool get_trbe_flag_update(u64 trbidr)
> +{
> + return trbidr & TRBIDR_FLAG;
> +}
> +
> +static inline bool is_trbe_programmable(u64 trbidr)
> +{
> + return !(trbidr & TRBIDR_PROG);
> +}
> +
> +static inline int get_trbe_address_align(u64 trbidr)
> +{
> + return (trbidr >> TRBIDR_ALIGN_SHIFT) & TRBIDR_ALIGN_MASK;
> +}
> +
> +static inline unsigned long get_trbe_write_pointer(void)
> +{
> + u64 trbptr = read_sysreg_s(SYS_TRBPTR_EL1);
> + unsigned long addr = (trbptr >> TRBPTR_PTR_SHIFT) & TRBPTR_PTR_MASK;

You don't need this shifting and masking. trbptr_el1 is a whole 64bit register

> +
> + return addr;
> +}
> +
> +static inline void set_trbe_write_pointer(unsigned long addr)
> +{
> + WARN_ON(is_trbe_enabled());
> + addr = (addr >> TRBPTR_PTR_SHIFT) & TRBPTR_PTR_MASK;

Same as above.

> + write_sysreg_s(addr, SYS_TRBPTR_EL1);
> +}
> +
> +static inline unsigned long get_trbe_limit_pointer(void)
> +{
> + u64 trblimitr = read_sysreg_s(SYS_TRBLIMITR_EL1);
> + unsigned long limit = (trblimitr >> TRBLIMITR_LIMIT_SHIFT) & TRBLIMITR_LIMIT_MASK;
> + unsigned long addr = limit << TRBLIMITR_LIMIT_SHIFT;
> +
> + WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));
> + return addr;
> +}
> +
> +static inline unsigned long get_trbe_base_pointer(void)
> +{
> + u64 trbbaser = read_sysreg_s(SYS_TRBBASER_EL1);

> + unsigned long addr = (trbbaser >> TRBBASER_BASE_SHIFT) & TRBBASER_BASE_MASK;
> +
> + addr = addr << TRBBASER_BASE_SHIFT;

nit: Could we instead do :

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 << TRBLIMITR_LIMIT_SHIFT)));

TRBBASER_BASE_SHIFT ?

> + WARN_ON(!IS_ALIGNED(addr, PAGE_SIZE));
> + write_sysreg_s(addr, SYS_TRBBASER_EL1);
> +}
>

Suzuki