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SubjectRe: [PATCH v4 4/7] drm: rcar-du: lvds: Allow for even and odd pixels swap
Hi Fabrizio,

Thank you for the patch.

On Fri, Dec 06, 2019 at 04:32:51PM +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.castro@bp.renesas.com>
>
> ---
> v3->v4:
> * New patch extracted from patch:
> "drm: rcar-du: lvds: Add dual-LVDS panels support"
> ---
> drivers/gpu/drm/rcar-du/rcar_lvds.c | 46 +++++++++++++++++++++++++++++--------
> 1 file changed, 37 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> index 6c1f171..cb2147c 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> @@ -71,6 +71,7 @@ struct rcar_lvds {
>
> struct drm_bridge *companion;
> bool dual_link;
> + bool stripe_swap_data;

Should we merge those two fields in an int dual_link that would be set
to DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS,
DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS or a negative value (or maybe we the
value of enum drm_lvds_dual_link_pixels could be modified so that 0
could mean single link) ?

> };
>
> #define bridge_to_rcar_lvds(b) \
> @@ -441,12 +442,20 @@ 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.
> + *
> + * ST_SWAP from LVD1STRIPE is reserved, do not set
> + * in the companion LVDS

Maybe "ST_SWAP is reserved for the companion encoder, only set it in the
primary encoder." ?

> + */
> + lvdstripe = LVDSTRIPE_ST_ON |
> + (lvds->companion && lvds->stripe_swap_data ?
> + LVDSTRIPE_ST_SWAP : 0);

To match the coding style of the rest of the driver,

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

Even though not strictly required, could you surround this statement
with { } as it spans quite a few lines with the comment ?

> + rcar_lvds_write(lvds, LVDSTRIPE, lvdstripe);
> }
>
> /*
> @@ -702,17 +711,33 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
> dual_link = drm_of_lvds_get_dual_link_pixel_order(p0, p1);
> of_node_put(p0);
> of_node_put(p1);
> - if (dual_link >= DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS) {
> +
> + switch (dual_link) {
> + case DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS:
> + /*
> + * By default we generate even pixels from this encoder and odd
> + * pixels from the companion encoder, but since p0 is connected
> + * to the port expecting ood pixels, and p1 is connected to the
> + * port expecting even pixels, we need to swap even and odd
> + * pixels around.
> + */
> + lvds->stripe_swap_data = true;
> + lvds->dual_link = true;
> + break;
> + case DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS:
> lvds->dual_link = true;
> - } else if (lvds->next_bridge && lvds->next_bridge->timings) {
> + 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.
> */
> - lvds->dual_link = lvds->next_bridge->timings->dual_link;
> + if (lvds->next_bridge && lvds->next_bridge->timings)
> + lvds->dual_link = lvds->next_bridge->timings->dual_link;
> }
>
> +

A single blank line is enough.

> if (!lvds->dual_link) {
> dev_dbg(dev, "Single-link configuration detected\n");
> goto done;
> @@ -728,6 +753,9 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
> "Dual-link configuration detected (companion encoder %pOF)\n",
> companion);
>
> + if (lvds->stripe_swap_data)
> + dev_dbg(dev, "Data swapping required\n");
> +
> companion_lvds = bridge_to_rcar_lvds(lvds->companion);
>
> /*

--
Regards,

Laurent Pinchart

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