Hi Biju, Thank you for the patch. On Sat, Apr 23, 2022 at 08:37:28AM +0100, Biju Das wrote: > From: LUU HOAI <hoai.luu.ub@xxxxxxxxxxx> > > In Gen3, when Alpha blend is enabled in the PnMR register, > depending on the initial value of the PnALPHAR register, > either channel of DU might be black screen. > Therefore, this patch prevents the black screen by setting > the PnALPHAR register to all 0. > > In addition, PnALPHAR register will be released in > the R-Car Gen3 Hardware Manual Rev 2.4 (Sep. 2021). > > Signed-off-by: LUU HOAI <hoai.luu.ub@xxxxxxxxxxx> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx> > --- > This patch is based on [1] > [1] https://github.com/renesas-rcar/linux-bsp/commit/fcb34fe338cbde0a64919430733541035f20a784 > > Not sure this patches has to go with Fixes tag for stable?? > > Tested the changes on RZ/G2M board > > root@hihope-rzg2m:/cip-test-scripts# modetest -M rcar-du -w 54:alpha:55555 > root@hihope-rzg2m:/cip-test-scripts# modetest -M rcar-du -s "93@90:1024x768@AR24" -d -P "54@90:400x300+200+200@XR24" > setting mode 1024x768-75Hz@AR24 on connectors 93, crtc 90 > testing 400x300@XR24 overlay plane 54 > --- > drivers/gpu/drm/rcar-du/rcar_du_plane.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/rcar-du/rcar_du_plane.c > index 5c1c7bb04f3f..aff39b9253f8 100644 > --- a/drivers/gpu/drm/rcar-du/rcar_du_plane.c > +++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.c > @@ -510,6 +510,12 @@ static void rcar_du_plane_setup_format_gen3(struct rcar_du_group *rgrp, > > rcar_du_plane_write(rgrp, index, PnDDCR4, > state->format->edf | PnDDCR4_CODE); > + > + /* In Gen3, PnALPHAR register need to be set to 0 > + * to avoid black screen issue when alpha blend is enable > + * on DU module > + */ Comments should start with /* on a line of its own, and you can also reflow the text to 80 columns: /* * In Gen3, PnALPHAR register need to be set to 0 to avoid black screen * issue when alpha blend is enable on DU module. */ It would however be nicer to document the exact behaviour, but the latest version of the documentation I have access to is rev 2.3 and it lists PnALPHAR as not available on Gen3. Furthermore, is this really the right fix, shouldn't we instead avoid enabling alpha-blending in PnMR on Gen3 ? > + rcar_du_plane_write(rgrp, index, PnALPHAR, 0x00000000); > } > > static void rcar_du_plane_setup_format(struct rcar_du_group *rgrp, -- Regards, Laurent Pinchart
