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>

---
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;
 };
 
 #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
+                        */
+                       lvdstripe = LVDSTRIPE_ST_ON |
+                               (lvds->companion && lvds->stripe_swap_data ?
+                                LVDSTRIPE_ST_SWAP : 0);
+               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;
        }
 
+
        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);
 
        /*
-- 
2.7.4

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