Quoting Biju Das (2022-04-26 09:41:57) > From: LUU HOAI <hoai.luu.ub@xxxxxxxxxxx> > > As per R-Car-Gen3_Common_OPC_Customer_Notifications_V30.1.pdf, > unexpected image output(such as incorrect colors or planes being > invisible) can happen on the below conditions, as PnALPHAR register > is not initialized by reset. > > When alpha blending (PpMRm.PpSPIM=0b101) is performed and: > •two Planes are enabled on any DUn (n=0,1,2,3) > oDSPRn= 0x0000 0031 or 0x0000 0013 > •or DU0 and DU1 is used for display at the same time > oDSPR0= 0x0000 0001 and DSPR1= 0x0000 0003 > oDSPR0= 0x0000 0003 and DSPR1= 0x0000 0001 > •or DU2 and DU3(H3 Only) is used for display at the same time > oDSPR2= 0x0000 0001 and DSPR3= 0x0000 0003 > oDSPR2= 0x0000 0003 and DSPR3= 0x0000 0001 > > This patch set PnALPHAR register to 0 to avoid this issue. > > Signed-off-by: LUU HOAI <hoai.luu.ub@xxxxxxxxxxx> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx> > --- > v1->v2: > * Updated commit description > * Updated the code comments > --- > drivers/gpu/drm/rcar-du/rcar_du_plane.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/rcar-du/rcar_du_plane.c > index f214a8b6cfd3..aa80c44dd8d7 100644 > --- a/drivers/gpu/drm/rcar-du/rcar_du_plane.c > +++ b/drivers/gpu/drm/rcar-du/rcar_du_plane.c > @@ -510,6 +510,18 @@ 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); > + > + /* > + * On Gen3, some DU channels have two planes, each being wired to a > + * separate VSPD instance. The DU can then blend two planes. While > + * this feature isn't used by the driver, issues related to alpha > + * blending (such as incorrect colors or planes being invisible) may > + * still occur if the PnALPHAR register has a stale value. Set the > + * register to 0 to avoid this. > + */ > + Sounds reasonable. > + /* TODO: Check if alpha-blending should be disabled in PnMR. */ How will this be done? Do you have a specific test in mind to determine if it causes issues? Or does it need validating through the hardware teams? > + rcar_du_plane_write(rgrp, index, PnALPHAR, 0); Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx> > } > > static void rcar_du_plane_setup_format(struct rcar_du_group *rgrp, > -- > 2.25.1 >
