> 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 <hl@xxxxxxxxxxxxxx> > Reviewed-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx> Acked-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> 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(+) >
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