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>

drivers/perf/Kconfig

@@ -71,6 +71,14 @@ config ARM_DSU_PMU
 	  system, control logic. The PMU allows counting various events related
 	  to DSU.
 
+config FSL_IMX8_DDR_PMU
+	tristate "Freescale i.MX8 DDR perf monitor"
+	depends on ARCH_MXC
+	  help
+	  Provides support for the DDR performance monitor in i.MX8, which
+	  can give information about memory throughput and other related
+	  events.
+
 config HISI_PMU
        bool "HiSilicon SoC PMU"
        depends on ARM64 && ACPI

drivers/perf/Makefile

@@ -5,6 +5,7 @@ obj-$(CONFIG_ARM_DSU_PMU) += arm_dsu_pmu.o
 obj-$(CONFIG_ARM_PMU) += arm_pmu.o arm_pmu_platform.o
 obj-$(CONFIG_ARM_PMU_ACPI) += arm_pmu_acpi.o
 obj-$(CONFIG_ARM_SMMU_V3_PMU) += arm_smmuv3_pmu.o
+obj-$(CONFIG_FSL_IMX8_DDR_PMU) += fsl_imx8_ddr_perf.o
 obj-$(CONFIG_HISI_PMU) += hisilicon/
 obj-$(CONFIG_QCOM_L2_PMU)	+= qcom_l2_pmu.o
 obj-$(CONFIG_QCOM_L3_PMU) += qcom_l3_pmu.o