Re: [PATCH v3] Added perf functionality to mmdc driver

From: Suzuki K Poulose
Date: Wed Aug 31 2016 - 09:08:40 EST

On 17/08/16 20:42, Zhengyu Shen wrote:
MMDC is a multi-mode DDR controller that supports DDR3/DDR3L x16/x32/x64
and LPDDR2 two channel x16/x32 memory types. MMDC is configurable, high
performance, and optimized. MMDC is present on i.MX6 Quad and i.MX6
QuadPlus devices, but this driver only supports i.MX6 Quad at the moment.
MMDC provides registers for performance counters which read via this
driver to help debug memory throughput and similar issues.

$ perf stat -a -e mmdc/busy-cycles/,mmdc/read-accesses/,mmdc/read-bytes/,mmdc/total-cycles/,mmdc/write-accesses/,mmdc/write-bytes/ dd if=/dev/zero of=/dev/null bs=1M count=5000
Performance counter stats for 'dd if=/dev/zero of=/dev/null bs=1M count=5000':

898021787 mmdc/busy-cycles/
14819600 mmdc/read-accesses/
471.30 MB mmdc/read-bytes/
2815419216 mmdc/total-cycles/
13367354 mmdc/write-accesses/
427.76 MB mmdc/write-bytes/

5.334757334 seconds time elapsed

Signed-off-by: Zhengyu Shen <zhengyu.shen@xxxxxxx>
Signed-off-by: Frank Li <>
Changes from v2 to v3:
Use WARN_ONCE instead of returning generic error values
Replace CPU Notifiers with newer state machine hotplug
Added additional checks on event_init for grouping and sampling
Remove useless mmdc_enable_profiling function
Added comments
Moved start index of events from 0x01 to 0x00
Added a counter to pmu_mmdc to only stop hrtimer after all events are finished
Replace readl_relaxed and writel_relaxed with readl and writel
Removed duplicate update function
Used devm_kasprintf when naming mmdcs probed

Changes from v1 to v2:
Added cpumask and migration handling support to driver
Validated event during event_init
Added code to properly stop counters
Used perf_invalid_context instead of perf_sw_context
Added hrtimer to poll for overflow
Added better description
Added support for multiple mmdcs

Should we move all the PMU specific code under at least CONFIG_PERF_EVENTS ?