Hi Roman, 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] Isn't this an issue with kernel driver not waiting for DE2 FINISH IRQ, but for VBLANK IRQ from TCON instead, before allowing to write new set of register values? https://megous.com/dl/tmp/4fe35b3fc72ee7de.png I haven't checked if FINISH flag is set at time of VBLANK interrupt, so maybe this is not the issue. regards, o. > [1]: https://github.com/GloDroid/glodroid_tests/issues/4 > 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); > + > struct de2_fmt_info { > u32 drm_fmt; > u32 de2_fmt; > diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c > index 662ba1018cc4..f005ab883503 100644 > --- a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c > +++ b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c > @@ -17,6 +17,8 @@ > #include "sun8i_vi_layer.h" > #include "sun8i_vi_scaler.h" > > +extern int sun8i_vi_keep_scaler_enabled; > + > static void sun8i_vi_layer_enable(struct sun8i_mixer *mixer, int channel, > int overlay, bool enable, unsigned int zpos) > { > @@ -149,7 +151,7 @@ static int sun8i_vi_layer_update_coord(struct sun8i_mixer *mixer, int channel, > */ > subsampled = format->hsub > 1 || format->vsub > 1; > > - if (insize != outsize || subsampled || hphase || vphase) { > + if (insize != outsize || subsampled || hphase || vphase || sun8i_vi_keep_scaler_enabled) { > unsigned int scanline, required; > struct drm_display_mode *mode; > u32 hscale, vscale, fps; > -- > 2.30.2 >
