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

Laurent Pinchart
2024-12-09T23:04:36Z

Hi Tomi,

Thank you for the patch.

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.

> ---
> 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