RE: [PATCH v10 5/5] drm/rockchip: Add dmc notifier in vop driver

when in ddr frequency scaling process, vop can not do enable or
disable operation, since in dcf we check vop clock to see whether
vop work. If vop work, dcf do ddr frequency scaling when vop
in vblank status, and we need to read vop register to check whether
vop go into vblank status. If vop not work, dcf can do ddr frequency
any time. So when do ddr frequency scaling, you disabled or enable
vop, there may two bad thing happen: 1, the panel flicker(when vop from
disable status change to enable). 2, kernel hang (when vop from enable
status change to disable, dcf need to read vblank status, but if you disable
vop clock, it can not get the status, it will lead soc dead) So we need
register to devfreq notifier, and we can get the dmc status. Also, when
there have two vop enabled, we need to disable dmc, since dcf only base
on one vop vblank time, so the other panel will flicker when do ddr
frequency scaling.

Signed-off-by: Lin Huang <redacted>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>

Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>


The code looks fine, but I've just found that I cannot merge this
code as I am not handling drivers/gpu/drm.

Please try to merge this piece into drivers/gpu/drm tree.

For the other 4 piecies (1/5 to 4/5) I'm ok with them. I'm merging them now.

---
Changes in v10:
- None

Changes in v9:
- None

Changes in v8:
- None

Changes in v7:
- None

Changes in v6:
- fix a build error

Changes in v5:
- improve some nits

Changes in v4:
- register notifier to devfreq_register_notifier
- use DEVFREQ_PRECHANGE and DEVFREQ_POSTCHANGE to get dmc status
- when two vop enable, disable dmc
- when two vop back to one vop, enable dmc

Changes in v3:
- when do vop eanble/disable, dmc will wait until it finish

Changes in v2:
- None

Changes in v1:
- use wait_event instead usleep

 drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 116 ++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)