On Fri, Jun 03, 2022 at 11:57:35AM +0300, Roman Stratiienko wrote: > Hi Maxime, > > пт, 3 июн. 2022 г. в 11:24, Maxime Ripard <maxime@xxxxxxxxxx>: > > > > Hi, > > > > On Thu, Jun 02, 2022 at 06:01:18PM +0000, Roman Stratiienko wrote: > > > According to DE2.0/DE3.0 manual VI scaler enable register is double > > > buffered, but de facto it doesn't, or the hardware has the shadow > > > register latching issues which causes single-frame picture corruption > > > after changing the state of scaler enable register. > > > > > > Allow the user to keep the scaler always enabled, preventing the UI > > > glitches on the transition from scaled to unscaled state. > > > > > > NOTE: > > > UI layer scaler has more registers with double-buffering issue and can't > > > be workarounded in the same manner. > > > > > > You may find a python test and a demo video for this issue at [1] > > > > > > [1]: https://github.com/GloDroid/glodroid_tests/issues/4 > > > > Please describe the issue entirely here. The commit log must be self-sufficient. > > Commit message already states "single-frame picture corruption after > changing the state of scaler enable register", therefore I find it > already self-sufficient > > Also I find demo videos and link to tests useful for the followers to > go further with investigation. Until a couple of years, where that URL isn't valid anymore and it's just useless. > If you have something specific in mind when asking to enhance the > commit message please say it. What sequence of events trigger the issue, what issue it triggers and why your solution addresses it would be nice > > > Signed-off-by: Roman Stratiienko <r.stratiienko@xxxxxxxxx> > > > --- > > > drivers/gpu/drm/sun4i/sun8i_mixer.c | 12 ++++++++++++ > > > drivers/gpu/drm/sun4i/sun8i_vi_layer.c | 4 +++- > > > 2 files changed, 15 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c b/drivers/gpu/drm/sun4i/sun8i_mixer.c > > > index 71ab0a00b4de..15cad0330f66 100644 > > > --- a/drivers/gpu/drm/sun4i/sun8i_mixer.c > > > +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c > > > @@ -27,6 +27,18 @@ > > > #include "sun8i_vi_layer.h" > > > #include "sunxi_engine.h" > > > > > > +/* According to DE2.0/DE3.0 manual VI scaler enable register is double > > > + * buffered, but de facto it doesn't, or the hardware has the shadow > > > + * register latching issues which causes single-frame picture corruption > > > + * after changing the state of scaler enable register. > > > + * Allow the user to keep the scaler always enabled, preventing the UI > > > + * glitches on the transition from scaled to unscaled state. > > > + */ > > > +int sun8i_vi_keep_scaler_enabled; > > > +MODULE_PARM_DESC(keep_vi_scaler_enabled, > > > + "Keep VI scaler enabled (1 = enabled, 0 = disabled (default))"); > > > +module_param_named(keep_vi_scaler_enabled, sun8i_vi_keep_scaler_enabled, int, 0644); > > > + > > > > It's not clear to me why we would want to make that a parameter? > > > >1 If it never works, we should fix it once and for all and not allow a broken setup at all. > > It's a hardware issue and can be fixed only within the hardware. > > Current patch is a workaround that if enabled can cause increased > power consumption for existing users. Therefore I think it is better > to give existing distro-maintainers a chance to test it prior to > delivery. Except distro-maintainers are likely never going to notice that flag exists in the first place, won't be using it and thus the issue will remain. Maxime
