Re: [PATCH v3 02/10] drm/rcar-du: Write DPTSR only if the second source exists

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Dec 10, 2024 at 01:04:19AM +0200, Laurent Pinchart wrote:
> On Fri, Dec 06, 2024 at 11:32:35AM +0200, Tomi Valkeinen wrote:
> > From: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
> > 
> > Currently the driver always writes DPTSR when setting up the hardware.
> > However, writing the register is only meaningful when the second source
> > for a plane is used, and the register is not even documented for SoCs
> > that do not have the second source.
> 
> I've confirmed that for all the models currently supported by the DU
> driver.
> 
> > So move the write behind a condition.
> > 
> > Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> 
> I will test the series on an M3N board.

Tested-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com> # On R-Car M3-N

> > ---
> >  drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c | 20 +++++++++++++++-----
> >  1 file changed, 15 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c b/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
> > index 2ccd2581f544..1ec806c8e013 100644
> > --- a/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
> > +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_du_group.c
> > @@ -185,11 +185,21 @@ static void rcar_du_group_setup(struct rcar_du_group *rgrp)
> >  		dorcr |= DORCR_PG1T | DORCR_DK1S | DORCR_PG1D_DS1;
> >  	rcar_du_group_write(rgrp, DORCR, dorcr);
> >  
> > -	/* Apply planes to CRTCs association. */
> > -	mutex_lock(&rgrp->lock);
> > -	rcar_du_group_write(rgrp, DPTSR, (rgrp->dptsr_planes << 16) |
> > -			    rgrp->dptsr_planes);
> > -	mutex_unlock(&rgrp->lock);
> > +	/*
> > +	 * DPTSR is used to select the source for the planes of a group. The
> > +	 * first source is chosen by writing 0 to the respective bits, and this
> > +	 * is always the default value of the register. In other words, writing
> > +	 * DPTSR is only needed if the SoC supports choosing the second source.
> > +	 *
> > +	 * The SoCs documentations seems to confirm this, as the DPTSR register
> > +	 * is not documented if only the first source exists on that SoC.
> > +	 */
> > +	if (rgrp->channels_mask & BIT(1)) {
> > +		mutex_lock(&rgrp->lock);
> > +		rcar_du_group_write(rgrp, DPTSR, (rgrp->dptsr_planes << 16) |
> > +				    rgrp->dptsr_planes);
> > +		mutex_unlock(&rgrp->lock);
> > +	}
> >  }
> >  
> >  /*
> > 

-- 
Regards,

Laurent Pinchart