History log of /linux-master/drivers/perf/fsl_imx8_ddr_perf.c
Revision Date Author Comments
# 1bb63938 15-Dec-2023 Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

perf: fsl_imx8_ddr: Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.

To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/c5b76bf352385d8ef6211ee8c43352c74eee064d.1702648125.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Will Deacon <will@kernel.org>


# 46fe448e 20-Nov-2023 Xu Yang <xu.yang_2@nxp.com>

perf: fsl_imx8_ddr: Add driver support for i.MX8DXL DDR Perf

Add driver support for i.MX8DXL DDR Perf, which supports AXI ID PORT
CHANNEL filter.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20231120093317.2652866-4-xu.yang_2@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>


# afd83967 20-Nov-2023 Xu Yang <xu.yang_2@nxp.com>

perf: fsl_imx8_ddr: Add AXI ID PORT CHANNEL filter support

This is the extension of AXI ID filter.

Filter is defined with 2 configuration registers per counter 1-3 (counter
0 is not used for filtering and lacks these registers).
* Counter N MASK COMP register - AXI_ID and AXI_MASKING.
* Counter N MUX CNTL register - AXI CHANNEL and AXI PORT.
-- 0: address channel
-- 1: data channel

This filter is exposed to userspace as an additional (channel, port) pair.
The definition of axi_channel is inverted in userspace, and it will be
reverted in driver automatically.

AXI filter of Perf Monitor in DDR Subsystem, only a single port0 exist, so
axi_port is reserved which should be 0.

e.g.
perf stat -a -e imx8_ddr0/axid-read,axi_mask=0xMMMM,axi_id=0xDDDD,axi_channel=0xH/ cmd
perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD,axi_channel=0xH/ cmd

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20231120093317.2652866-1-xu.yang_2@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>


# f4e2bd91 10-Aug-2023 Xu Yang <xu.yang_2@nxp.com>

perf/imx_ddr: don't enable counter0 if none of 4 counters are used

In current driver, counter0 will be enabled after ddr_perf_pmu_enable()
is called even though none of the 4 counters are used. This will cause
counter0 continue to count until ddr_perf_pmu_disabled() is called. If
pmu is not disabled all the time, the pmu interrupt will be asserted
from time to time due to counter0 will overflow and irq handler will
clear it. It's not an expected behavior. This patch will not enable
counter0 if none of 4 counters are used.

Fixes: 9a66d36cc7ac ("drivers/perf: imx_ddr: Add DDR performance counter support to perf")
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20230811015438.1999307-2-xu.yang_2@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>


# e89ecd83 10-Aug-2023 Xu Yang <xu.yang_2@nxp.com>

perf/imx_ddr: speed up overflow frequency of cycle

For i.MX8MP, we cannot ensure that cycle counter overflow occurs at least
4 times as often as other events. Due to byte counters will count for any
event configured, it will overflow more often. And if byte counters
overflow that related counters would stop since they share the
COUNTER_CNTL. We can speed up cycle counter overflow frequency by setting
counter parameter (CP) field of cycle counter. In this way, we can avoid
stop counting byte counters when interrupt didn't come and the byte
counters can be fetched or updated from each cycle counter overflow
interrupt.

Because we initialize CP filed to shorten counter0 overflow time, the cycle
counter will start couting from a fixed/base value each time. We need to
remove the base from the result too. Therefore, we could get precise result
from cycle counter.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20230811015438.1999307-1-xu.yang_2@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>


# 918dc87b 14-Jul-2023 Rob Herring <robh@kernel.org>

drivers/perf: Explicitly include correct DT includes

The DT of_device.h and of_platform.h date back to the separate
of_platform_bus_type before it as merged into the regular platform bus.
As part of that merge prepping Arm DT support 13 years ago, they
"temporarily" include each other. They also include platform_device.h
and of.h. As a result, there's a pretty much random mix of those include
files used throughout the tree. In order to detangle these headers and
replace the implicit includes with struct declarations, users need to
explicitly include the correct includes.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230714174832.4061752-1-robh@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>


# 7f49b037 03-Feb-2023 Sascha Hauer <s.hauer@pengutronix.de>

drivers/perf: fsl_imx8_ddr_perf: Remove set-but-not-used variable

active_events is set but not used, remove it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Link: https://lore.kernel.org/r/20230203121509.3580245-1-s.hauer@pengutronix.de
Signed-off-by: Will Deacon <will@kernel.org>


# 49785a77 19-May-2022 keliu <liuke94@huawei.com>

drivers/perf: Directly use ida_alloc()/free()

Use ida_alloc()/ida_free() instead of deprecated
ida_simple_get()/ida_simple_remove() .

Signed-off-by: keliu <liuke94@huawei.com>
Link: https://lore.kernel.org/r/20220519080127.147030-1-liuke94@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>


# d02b4dd8 05-Apr-2022 Borislav Petkov <bp@suse.de>

perf/imx_ddr: Fix undefined behavior due to shift overflowing the constant

Fix:

In file included from <command-line>:0:0:
In function ‘ddr_perf_counter_enable’,
inlined from ‘ddr_perf_irq_handler’ at drivers/perf/fsl_imx8_ddr_perf.c:651:2:
././include/linux/compiler_types.h:352:38: error: call to ‘__compiletime_assert_729’ \
declared with attribute error: FIELD_PREP: mask is not constant
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
...

See https://lore.kernel.org/r/YkwQ6%2BtIH8GQpuct@zn.tnic for the gory
details as to why it triggers with older gccs only.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Frank Li <Frank.li@nxp.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220405151517.29753-10-bp@alien8.de
Signed-off-by: Will Deacon <will@kernel.org>


# d96b1b8c 17-Jun-2021 Jing Xiangfeng <jingxiangfeng@huawei.com>

drivers/perf: fix the missed ida_simple_remove() in ddr_perf_probe()

ddr_perf_probe() misses to call ida_simple_remove() in an error path.
Jump to cpuhp_state_err to fix it.

Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Link: https://lore.kernel.org/r/20210617122614.166823-1-jingxiangfeng@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>


# 773510f4 09-Jun-2021 Qi Liu <liuqi115@huawei.com>

drivers/perf: Simplify EVENT ATTR macro in fsl_imx8_ddr_perf.c

Use common macro PMU_EVENT_ATTR_ID to simplify IMX8_DDR_PMU_EVENT_ATTR

Reviewed by Frank Li <Frank .li@nxp.com>

Cc: Frank Li <Frank.li@nxp.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Qi Liu <liuqi115@huawei.com>
Link: https://lore.kernel.org/r/1623220863-58233-7-git-send-email-liuqi115@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>


# ba4489fb 18-May-2021 Thomas Gleixner <tglx@linutronix.de>

perf/imx_ddr: Use irq_set_affinity()

The driver uses irq_set_affinity_hint() to set the affinity for the PMU
interrupts, which relies on the undocumented side effect that this function
actually sets the affinity under the hood.

Setting an hint is clearly not a guarantee and for these PMU interrupts an
affinity hint, which is supposed to guide userspace for setting affinity,
is beyond pointless, because the affinity of these interrupts cannot be
modified from user space.

Aside of that the error checks are bogus because the only error which is
returned from irq_set_affinity_hint() is when there is no irq descriptor
for the interrupt number, but not when the affinity set fails. That's on
purpose because the hint can point to an offline CPU.

Replace the mindless abuse with irq_set_affinity().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Frank Li <Frank.li@nxp.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210518093118.699566062@linutronix.de
Signed-off-by: Will Deacon <will@kernel.org>


# fb62d675 19-Mar-2021 Qi Liu <liuqi115@huawei.com>

drivers/perf: convert sysfs sprintf family to sysfs_emit

sprintf does not know the PAGE_SIZE maximum of the temporary buffer
used for sysfs content and it's possible to overrun the buffer length.

Use sysfs_emit() function to ensures that no overrun is done.

Signed-off-by: Qi Liu <liuqi115@huawei.com>
Link: https://lore.kernel.org/r/1616148273-16374-4-git-send-email-liuqi115@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>


# 700a9cf0 19-Mar-2021 Zihao Tang <tangzihao1@hisilicon.com>

drivers/perf: convert sysfs snprintf family to sysfs_emit

Fix the following coccicheck warning:

./drivers/perf/hisilicon/hisi_uncore_pmu.c:128:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/fsl_imx8_ddr_perf.c:173:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm_spe_pmu.c:129:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm_smmu_pmu.c:563:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm_dsu_pmu.c:149:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm_dsu_pmu.c:139:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm-cmn.c:563:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm-cmn.c:351:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm-ccn.c:224:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm-cci.c:708:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm-cci.c:699:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm-cci.c:528:8-16: WARNING: use scnprintf or sprintf.
./drivers/perf/arm-cci.c:309:8-16: WARNING: use scnprintf or sprintf.

Signed-off-by: Zihao Tang <tangzihao1@hisilicon.com>
Signed-off-by: Qi Liu <liuqi115@huawei.com>
Link: https://lore.kernel.org/r/1616148273-16374-2-git-send-email-liuqi115@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>


# 3cb7d2da 17-Jan-2021 Rikard Falkeborn <rikard.falkeborn@gmail.com>

perf/imx_ddr: Constify static struct attribute_group

The only usage is to put their addresses in an array of pointers to
const struct attribute group. Make them const to allow the compiler
to put them in read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20210117212847.21319-3-rikard.falkeborn@gmail.com
Signed-off-by: Will Deacon <will@kernel.org>


# 881b0520 30-Nov-2020 Joakim Zhang <qiangqing.zhang@nxp.com>

perf/imx_ddr: Add system PMU identifier for userspace

The DDR Perf for i.MX8 is a system PMU whose AXI ID would different from
SoC to SoC. Need expose system PMU identifier for userspace which refer
to /sys/bus/event_source/devices/<PMU DEVICE>/identifier.

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20201130114202.26057-3-qiangqing.zhang@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>


# 6b46338f 27-Oct-2020 Joakim Zhang <qiangqing.zhang@nxp.com>

perf/imx_ddr: Add stop event counters support for i.MX8MP

DDR Perf driver only supports free-running event counters(counter1/2/3)
now, this patch adds support for stop event counters.

Legacy SoCs:
Cycle counter(counter0) is a special counter, only count cycles. When
cycle counter overflow, it will lock all counters and generate an
interrupt. In ddr_perf_irq_handler, disable cycle counter then all
counters would stop at the same time, update all counters' count, then
enable cycle counter that all counters count again. During this process,
only clear cycle counter, no need to clear event counters since they are
free-running counters. They would continue counting after overflow and
do/while loop from ddr_perf_event_update can handle event counters
overflow case.

i.MX8MP:
Almost all is the same as legacy SoCs, the only difference is that, event
counters are not free-running any more. Like cycle counter, when event
counters overflow, they would stop counting unless clear the counter,
and no interrupt generate for event counters. So we should clear event
counters that let them re-count when cycle counter overflow, which ensure
event counters will not lose data.

This patch adds stop event counters support which would be compatible to
free-running event counters. We use the cycle counter to stop overflow
of the event counters.

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Link: https://lore.kernel.org/r/20201027104451.15434-1-qiangqing.zhang@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>


# f32ed8eb 17-Jul-2020 Qi Liu <liuqi115@huawei.com>

drivers/perf: Prevent forced unbinding of PMU drivers

Forcefully unbinding PMU drivers during perf sampling will lead to
a kernel panic, because the perf upper-layer framework call a NULL
pointer in this situation.

To solve this issue, "suppress_bind_attrs" should be set to true, so
that bind/unbind can be disabled via sysfs and prevent unbinding PMU
drivers during perf sampling.

Signed-off-by: Qi Liu <liuqi115@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1594975763-32966-1-git-send-email-liuqi115@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>


# bdc5c744 16-Jul-2020 Qi Liu <liuqi115@huawei.com>

drivers/perf: Fix kernel panic when rmmod PMU modules during perf sampling

When users try to remove PMU modules during perf sampling, kernel panic
will happen because the pmu->read() is a NULL pointer here.

INFO on HiSilicon hip08 platform as follow:
pc : hisi_uncore_pmu_event_update+0x30/0xa4 [hisi_uncore_pmu]
lr : hisi_uncore_pmu_read+0x20/0x2c [hisi_uncore_pmu]
sp : ffff800010103e90
x29: ffff800010103e90 x28: ffff0027db0c0e40
x27: ffffa29a76f129d8 x26: ffffa29a77ceb000
x25: ffffa29a773a5000 x24: ffffa29a77392000
x23: ffffddffe5943f08 x22: ffff002784285960
x21: ffff002784285800 x20: ffff0027d2e76c80
x19: ffff0027842859e0 x18: ffff80003498bcc8
x17: ffffa29a76afe910 x16: ffffa29a7583f530
x15: 16151a1512061a1e x14: 0000000000000000
x13: ffffa29a76f1e238 x12: 0000000000000001
x11: 0000000000000400 x10: 00000000000009f0
x9 : ffff8000107b3e70 x8 : ffff0027db0c1890
x7 : ffffa29a773a7000 x6 : 00000007f5131013
x5 : 00000007f5131013 x4 : 09f257d417c00000
x3 : 00000002187bd7ce x2 : ffffa29a38f0f0d8
x1 : ffffa29a38eae268 x0 : ffff0027d2e76c80
Call trace:
hisi_uncore_pmu_event_update+0x30/0xa4 [hisi_uncore_pmu]
hisi_uncore_pmu_read+0x20/0x2c [hisi_uncore_pmu]
__perf_event_read+0x1a0/0x1f8
flush_smp_call_function_queue+0xa0/0x160
generic_smp_call_function_single_interrupt+0x18/0x20
handle_IPI+0x31c/0x4dc
gic_handle_irq+0x2c8/0x310
el1_irq+0xcc/0x180
arch_cpu_idle+0x4c/0x20c
default_idle_call+0x20/0x30
do_idle+0x1b4/0x270
cpu_startup_entry+0x28/0x30
secondary_start_kernel+0x1a4/0x1fc

To solve the above issue, current module should be registered to kernel,
so that try_module_get() can be invoked when perf sampling starts. This
adds the reference counting of module and could prevent users from removing
modules during sampling.

Reported-by: Haifeng Wang <wang.wanghaifeng@huawei.com>
Signed-off-by: Qi Liu <liuqi115@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1594891165-8228-1-git-send-email-liuqi115@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>


# 049d9191 25-Feb-2020 Joakim Zhang <qiangqing.zhang@nxp.com>

drivers/perf: fsl_imx8_ddr: Correct the CLEAR bit definition

When disabling a counter from ddr_perf_event_stop(), the counter value
is reset to 0 at the same time.

Preserve the counter value by performing a read-modify-write of the
PMU register and clearing only the enable bit.

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Will Deacon <will@kernel.org>


# 9ee68b31 14-Jan-2020 Leonard Crestez <leonard.crestez@nxp.com>

perf/imx_ddr: Fix cpu hotplug state cleanup

This driver allocates a dynamic cpu hotplug state but never releases it.
If reloaded in a loop it will quickly trigger a WARN message:

"No more dynamic states available for CPU hotplug"

Fix by calling cpuhp_remove_multi_state on remove like several other
perf pmu drivers.

Also fix the cleanup logic on probe error paths: add the missing
cpuhp_remove_multi_state call and properly check the return value from
cpuhp_state_add_instant_nocalls.

Fixes: 9a66d36cc7ac ("drivers/perf: imx_ddr: Add DDR performance counter support to perf")
Acked-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Will Deacon <will@kernel.org>


# f1d303a1 04-Nov-2019 Joakim Zhang <qiangqing.zhang@nxp.com>

perf/imx_ddr: Dump AXI ID filter info to userspace

caps/filter indicates whether HW supports AXI ID filter or not.
caps/enhanced_filter indicates whether HW supports enhanced AXI ID filter
or not.

Users can check filter features from userspace with these attributions.

Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
[will: reworked cap switch to be less error-prone]
Signed-off-by: Will Deacon <will@kernel.org>


# d3eeece9 01-Nov-2019 Joakim Zhang <qiangqing.zhang@nxp.com>

perf/imx_ddr: Add driver for DDR PMU in i.MX8MPlus

Add driver for DDR PMU in i.MX8MPlus.

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Will Deacon <will@kernel.org>


# 44f8bd01 01-Nov-2019 Joakim Zhang <qiangqing.zhang@nxp.com>

perf/imx_ddr: Add enhanced AXI ID filter support

With DDR_CAP_AXI_ID_FILTER quirk, indicating HW supports AXI ID filter
which only can get bursts from DDR transaction, i.e. DDR read/write
requests.

This patch add DDR_CAP_AXI_ID_ENHANCED_FILTER quirk, indicating HW
supports AXI ID filter which can get bursts and bytes from DDR
transaction at the same time. We hope PMU always return bytes in the
driver due to it is more meaningful for users.

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Will Deacon <will@kernel.org>


# c12c0288 27-Aug-2019 Joakim Zhang <qiangqing.zhang@nxp.com>

perf/imx_ddr: Add support for AXI ID filtering

AXI filtering is used by events 0x41 and 0x42 to count reads or writes
with an ARID or AWID matching a specified filter. The filter is exposed
to userspace as an (ID, MASK) pair, where each set bit in the mask
causes the corresponding bit in the ID to be ignored when matching
against the ID of memory transactions for the purposes of incrementing
the counter.

For example:

# perf stat -a -e imx8_ddr0/axid-read,axi_mask=0xff,axi_id=0x800/ cmd

will count all read transactions from AXI IDs 0x800 - 0x8ff. If the
'axi_mask' is omitted, then it is treated as 0x0 which means that the
'axi_id' will be matched exactly.

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Will Deacon <will@kernel.org>


# 4b9ace9c 04-Jul-2019 Leonard Crestez <leonard.crestez@nxp.com>

perf/imx_ddr: Add MODULE_DEVICE_TABLE

This is required for automatic probing when driver is built as a module.

Fixes: 9a66d36cc7ac ("drivers/perf: imx_ddr: Add DDR performance counter support to perf")
Acked-by: Frank Li <frank.li@nxp.com>
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Will Deacon <will@kernel.org>


# 9a66d36c 01-May-2019 Frank Li <frank.li@nxp.com>

drivers/perf: imx_ddr: Add DDR performance counter support to perf

Add DDR performance monitor support for iMX8QXP. The PMU consists of 3
programmable event counters and a single dedicated cycle counter.

Example usage:

$ perf stat -a -e \
imx8_ddr0/read-cycles/,imx8_ddr0/write-cycles/,imx8_ddr0/precharge/ ls

- or -

$ perf stat -a -e \
imx8_ddr0/cycles/,imx8_ddr0/read-access/,imx8_ddr0/write-access/ ls

Other events are supported, and advertised via perf list.

Reviewed-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
[will: rewrote commit message/kconfig and used #defines for dev/cpuhp names]
Signed-off-by: Will Deacon <will.deacon@arm.com>