Hi Kieran,
Subject: Re: [PATCH v2] drm: rcar-du: Fix Alpha blending issue on Gen3
Quoting Biju Das (2022-04-26 09:41:57)
From: LUU HOAI hoai.luu.ub@renesas.com
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@renesas.com Signed-off-by: Biju Das biju.das.jz@bp.renesas.com
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 toa
* 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. Setthe
* 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?
It is TO DO activity and will be investigated later. After investigation, if it is no more required Then will remove the above comment or if it is required will send a patch.
Cheers, Biju
rcar_du_plane_write(rgrp, index, PnALPHAR, 0);Reviewed-by: Kieran Bingham kieran.bingham+renesas@ideasonboard.com
}
static void rcar_du_plane_setup_format(struct rcar_du_group *rgrp,
2.25.1