linux-kernel - [RFC v2 0/1] drm: lima: devfreq and cooling device support

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Message-Id: <20191227173707.20413-1-martin.blumenstingl@googlemail.com>
Date:   Fri, 27 Dec 2019 18:37:06 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     yuq825@...il.com, dri-devel@...ts.freedesktop.org
Cc:     airlied@...ux.ie, daniel@...ll.ch, linux-kernel@...r.kernel.org,
        tomeu.vizoso@...labora.com, robh@...nel.org, steven.price@....com,
        alyssa.rosenzweig@...labora.com, linux-amlogic@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, wens@...e.org,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [RFC v2 0/1] drm: lima: devfreq and cooling device support

This is my attempt at adding devfreq (and cooling device) support to
the lima driver.

I am seeking comments in two general areas:
- regarding the integration into the existing lima code
- for the actual devfreq code (I had to adapt the panfrost code
  slightly, because lima uses a bus and a GPU/core clock)

My own TODO list includes "more" testing on various Amlogic SoCs.
So far I have tested this on Meson8b and Meson8m2 (which both have a
GPU OPP table defined). However, I still need to test this on a GXL
board (which is currently missing the GPU OPP table).

Test results from a Meson8m2 board:
TEST #1: glmark2-es2-drm --off-screen in an infinite loop while cycling
         through all available frequencies using the userspace governor

     From  :   To
           : 182142857 318750000 425000000 510000000 637500000   time(ms)
  182142857:         0      1274      1274      1273      1279   5399468
  318750000:      1274         0      1274      1273      1272   5114700
  425000000:      1276      1274         0      1272      1271   5122008
  510000000:      1909      1273      1273         0       636   5274292
* 637500000:       640      1272      1272      1273         0   5186796
Total transition : 24834

TEST #2: glmark2-es2-drm --off-screen in an infinite loop with the
         simple_ondemand governor
     From  :   To
           : 182142857 318750000 425000000 510000000 637500000   time(ms)
  182142857:         0         0         0         0       203    318328
  318750000:        53         0         0         0        21     56044
  425000000:        27        18         0         0         2     34172
  510000000:        27         6        14         0         1     41348
* 637500000:        95        50        33        48         0   2085312


Changes since RFC v1 at [0]:
- added lock to protect the statistics as these can be written 
  concurrently for example when the GP and PP IRQ are firing at the
  same time. Thanks to Qiang Yu for the suggestion!
- updated the copyright notice of lima_devfreq.c to indicate that the
  code is derived from panfrost_devfreq.c. Thanks to  Chen-Yu Tsai  for
  the suggestion!
- I did not unify the code with panfrost yet because I don't know where
  to put the result. any suggestion is welcome though!


[0] https://patchwork.freedesktop.org/series/70967/


Martin Blumenstingl (1):
  drm/lima: Add optional devfreq support

 drivers/gpu/drm/lima/Kconfig        |   1 +
 drivers/gpu/drm/lima/Makefile       |   3 +-
 drivers/gpu/drm/lima/lima_devfreq.c | 183 ++++++++++++++++++++++++++++
 drivers/gpu/drm/lima/lima_devfreq.h |  15 +++
 drivers/gpu/drm/lima/lima_device.c  |   4 +
 drivers/gpu/drm/lima/lima_device.h  |  17 +++
 drivers/gpu/drm/lima/lima_drv.c     |  14 ++-
 drivers/gpu/drm/lima/lima_sched.c   |   7 ++
 drivers/gpu/drm/lima/lima_sched.h   |   3 +
 9 files changed, 244 insertions(+), 3 deletions(-)
 create mode 100644 drivers/gpu/drm/lima/lima_devfreq.c
 create mode 100644 drivers/gpu/drm/lima/lima_devfreq.h

-- 
2.24.1