[PATCH v5 4/6] drm: rcar-du: lvds: Allow for even and odd pixels swap

[Fabrizio Castro]

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@xxxxxxxxxxxxxx>

---
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;
 };
 
 #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);
-- 
2.7.4