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SubjectRe: [PATCH/RFC 05/12] drm: rcar-du: lvds: Add data swap support
Hi Fabrizio,

Thank you for the patch.

On Fri, Aug 02, 2019 at 08:34:02AM +0100, Fabrizio Castro wrote:
> When in vertical stripe mode of operation, there is the option
> of swapping even data and odd data on the two LVDS interfaces
> used to drive the video output.
> Add data swap support by exposing a new DT property named
> "renesas,swap-data".
>
> Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> ---
> drivers/gpu/drm/rcar-du/rcar_lvds.c | 23 ++++++++++++++++-------
> 1 file changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> index 3aeaf9e..c306fab 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> @@ -69,6 +69,7 @@ struct rcar_lvds {
>
> struct drm_bridge *companion;
> bool dual_link;
> + bool stripe_swap_data;
> };
>
> #define bridge_to_rcar_lvds(bridge) \
> @@ -439,12 +440,16 @@ static void rcar_lvds_enable(struct drm_bridge *bridge)
> rcar_lvds_write(lvds, LVDCHCR, lvdhcr);
>
> if (lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK) {
> - /*
> - * Configure vertical stripe based on the mode of operation of
> - * the connected device.
> - */
> - rcar_lvds_write(lvds, LVDSTRIPE,
> - lvds->dual_link ? LVDSTRIPE_ST_ON : 0);
> + u32 lvdstripe = 0;
> +
> + if (lvds->dual_link)
> + /*
> + * Configure vertical stripe based on the mode of
> + * operation of the connected device.
> + */
> + lvdstripe = LVDSTRIPE_ST_ON | (lvds->stripe_swap_data ?
> + LVDSTRIPE_ST_SWAP : 0);

Would the following be simpler ?

lvdstripe = (lvds->dual_link ? LVDSTRIPE_ST_ON : 0)
| (lvds->stripe_swap_data ? LVDSTRIPE_ST_SWAP : 0);

> + rcar_lvds_write(lvds, LVDSTRIPE, lvdstripe);
> }
>
> /*
> @@ -770,8 +775,12 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
> }
> }
>
> - if (lvds->dual_link)
> + if (lvds->dual_link) {
> + lvds->stripe_swap_data = of_property_read_bool(
> + lvds->dev->of_node,
> + "renesas,swap-data");
> ret = rcar_lvds_parse_dt_companion(lvds);
> + }

As explained in the review of the corresponding DT bindings, I think
this should be queried from the remote device rather than specified in
DT.

>
> done:
> of_node_put(local_output);

--
Regards,

Laurent Pinchart

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