perf: add qcom l2 cache perf events driver

Adds perf events support for L2 cache PMU.

The L2 cache PMU driver is named 'l2cache_0' and can be used
with perf events to profile L2 events such as cache hits
and misses on Qualcomm Technologies processors.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>
[will: minimise nesting in l2_cache_associate_cpu_with_cluster]
[will: use kstrtoul for unsigned long, remove redunant .owner setting]
Signed-off-by: Will Deacon <will.deacon@arm.com>

Documentation/perf/qcom_l2_pmu.txt

@@ -0,0 +1,38 @@
+Qualcomm Technologies Level-2 Cache Performance Monitoring Unit (PMU)
+=====================================================================
+
+This driver supports the L2 cache clusters found in Qualcomm Technologies
+Centriq SoCs. There are multiple physical L2 cache clusters, each with their
+own PMU. Each cluster has one or more CPUs associated with it.
+
+There is one logical L2 PMU exposed, which aggregates the results from
+the physical PMUs.
+
+The driver provides a description of its available events and configuration
+options in sysfs, see /sys/devices/l2cache_0.
+
+The "format" directory describes the format of the events.
+
+Events can be envisioned as a 2-dimensional array. Each column represents
+a group of events. There are 8 groups. Only one entry from each
+group can be in use at a time. If multiple events from the same group
+are specified, the conflicting events cannot be counted at the same time.
+
+Events are specified as 0xCCG, where CC is 2 hex digits specifying
+the code (array row) and G specifies the group (column) 0-7.
+
+In addition there is a cycle counter event specified by the value 0xFE
+which is outside the above scheme.
+
+The driver provides a "cpumask" sysfs attribute which contains a mask
+consisting of one CPU per cluster which will be used to handle all the PMU
+events on that cluster.
+
+Examples for use with perf:
+
+  perf stat -e l2cache_0/config=0x001/,l2cache_0/config=0x042/ -a sleep 1
+
+  perf stat -e l2cache_0/config=0xfe/ -C 2 sleep 1
+
+The driver does not support sampling, therefore "perf record" will
+not work. Per-task perf sessions are not supported.

drivers/perf/Kconfig

@@ -12,6 +12,15 @@ config ARM_PMU
 	  Say y if you want to use CPU performance monitors on ARM-based
 	  systems.
 
+config QCOM_L2_PMU
+	bool "Qualcomm Technologies L2-cache PMU"
+	depends on ARCH_QCOM && ARM64 && PERF_EVENTS && ACPI
+	  help
+	  Provides support for the L2 cache performance monitor unit (PMU)
+	  in Qualcomm Technologies processors.
+	  Adds the L2 cache PMU into the perf events subsystem for
+	  monitoring L2 cache events.
+
 config XGENE_PMU
         depends on PERF_EVENTS && ARCH_XGENE
         bool "APM X-Gene SoC PMU"

drivers/perf/Makefile

@@ -1,2 +1,3 @@
 obj-$(CONFIG_ARM_PMU) += arm_pmu.o
+obj-$(CONFIG_QCOM_L2_PMU)	+= qcom_l2_pmu.o
 obj-$(CONFIG_XGENE_PMU) += xgene_pmu.o

include/linux/cpuhotplug.h

@@ -138,6 +138,7 @@ enum cpuhp_state {
 	CPUHP_AP_PERF_ARM_CCI_ONLINE,
 	CPUHP_AP_PERF_ARM_CCN_ONLINE,
 	CPUHP_AP_PERF_ARM_L2X0_ONLINE,
+	CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
 	CPUHP_AP_WORKQUEUE_ONLINE,
 	CPUHP_AP_RCUTREE_ONLINE,
 	CPUHP_AP_ONLINE_DYN,