Hi Fabrizio,

Thank you for the patch.

On Mon, Dec 16, 2019 at 08:12:32PM +0000, Fabrizio Castro wrote:
> DT properties dual-lvds-even-pixels and dual-lvds-odd-pixels
> can be used to work out if the driver needs to swap even
> and odd pixels around.
> 
> This patch makes use of the return value from function
> drm_of_lvds_get_dual_link_pixel_order to determine if we
> need to swap odd and even pixels around for things to work
> properly.
> 
> Signed-off-by: Fabrizio Castro <fabrizio.cas...@bp.renesas.com>
> 
> ---
> v4->v5:
> * Addressed comments from Laurent's review
> 
> v3->v4:
> * New patch extracted from patch:
>   "drm: rcar-du: lvds: Add dual-LVDS panels support"
> ---
>  drivers/gpu/drm/rcar-du/rcar_lvds.c | 67 
> +++++++++++++++++++++++++++++--------
>  1 file changed, 53 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c 
> b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> index 3eb208e..c6a38c3 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> @@ -37,6 +37,12 @@ enum rcar_lvds_mode {
>       RCAR_LVDS_MODE_VESA = 4,
>  };
>  
> +enum rcar_lvds_link_type {
> +     RCAR_LVDS_SINGLE_LINK = 0,
> +     RCAR_LVDS_DUAL_LINK_EVEN_ODD_PIXELS = 1,
> +     RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS = 2,
> +};
> +
>  #define RCAR_LVDS_QUIRK_LANES                BIT(0)  /* LVDS lanes 1 and 3 
> inverted */
>  #define RCAR_LVDS_QUIRK_GEN3_LVEN    BIT(1)  /* LVEN bit needs to be set on 
> R8A77970/R8A7799x */
>  #define RCAR_LVDS_QUIRK_PWD          BIT(2)  /* PWD bit available (all of 
> Gen3 but E3) */
> @@ -67,7 +73,7 @@ struct rcar_lvds {
>       } clocks;
>  
>       struct drm_bridge *companion;
> -     bool dual_link;
> +     enum rcar_lvds_link_type dual_link;

Do you think we should rename this to link_type (and test for
lvds->link_type != RCAR_LVDS_SINGLE_LINK) instead of lvds->dual_link) ?
Apart from that,

Reviewed-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>

>  };
>  
>  #define bridge_to_rcar_lvds(b) \
> @@ -484,12 +490,31 @@ static void rcar_lvds_atomic_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) {
> +                     /*
> +                      * By default we generate even pixels from the primary
> +                      * encoder and odd pixels from the companion encoder.
> +                      * Swap pixels around if the sink requires odd pixels
> +                      * from the primary encoder and even pixels from the
> +                      * companion encoder.
> +                      */
> +                     bool swap_pixels = lvds->dual_link ==
> +                             RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS;
> +
> +                     /*
> +                      * Configure vertical stripe since we are dealing with
> +                      * an LVDS dual-link connection.
> +                      *
> +                      * ST_SWAP is reserved for the companion encoder, only
> +                      * set it in the primary encoder.
> +                      */
> +                     lvdstripe = LVDSTRIPE_ST_ON
> +                               | (lvds->companion && swap_pixels ?
> +                                  LVDSTRIPE_ST_SWAP : 0);
> +             }
> +             rcar_lvds_write(lvds, LVDSTRIPE, lvdstripe);
>       }
>  
>       /*
> @@ -716,15 +741,26 @@ static int rcar_lvds_parse_dt_companion(struct 
> rcar_lvds *lvds)
>       of_node_put(port0);
>       of_node_put(port1);
>  
> -     if (dual_link >= DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS)
> -             lvds->dual_link = true;
> -     else if (lvds->next_bridge && lvds->next_bridge->timings)
> +     switch (dual_link) {
> +     case DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS:
> +             lvds->dual_link = RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS;
> +             break;
> +     case DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS:
> +             lvds->dual_link = RCAR_LVDS_DUAL_LINK_EVEN_ODD_PIXELS;
> +             break;
> +     default:
>               /*
>                * Early dual-link bridge specific implementations populate the
> -              * timings field of drm_bridge, read the dual_link flag off the
> -              * bridge directly for backward compatibility.
> +              * timings field of drm_bridge. If the flag is set, we assume
> +              * that we are expected to generate even pixels from the primary
> +              * encoder, and odd pixels from the companion encoder.
>                */
> -             lvds->dual_link = lvds->next_bridge->timings->dual_link;
> +             if (lvds->next_bridge && lvds->next_bridge->timings &&
> +                 lvds->next_bridge->timings->dual_link)
> +                     lvds->dual_link = RCAR_LVDS_DUAL_LINK_EVEN_ODD_PIXELS;
> +             else
> +                     lvds->dual_link = RCAR_LVDS_SINGLE_LINK;
> +     }
>  
>       if (!lvds->dual_link) {
>               dev_dbg(dev, "Single-link configuration detected\n");
> @@ -741,6 +777,9 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds 
> *lvds)
>               "Dual-link configuration detected (companion encoder %pOF)\n",
>               companion);
>  
> +     if (lvds->dual_link == RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS)
> +             dev_dbg(dev, "Data swapping required\n");
> +
>       /*
>        * FIXME: We should not be messing with the companion encoder private
>        * data from the primary encoder, we should rather let the companion
> @@ -751,7 +790,7 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds 
> *lvds)
>        * for the time being.
>        */
>       companion_lvds = bridge_to_rcar_lvds(lvds->companion);
> -     companion_lvds->dual_link = true;
> +     companion_lvds->dual_link = lvds->dual_link;
>  
>  done:
>       of_node_put(companion);

-- 
Regards,

Laurent Pinchart
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