drm/panel-simple: allow LVDS format override

Some panels support multiple LVDS data mapping formats, which can be
used e.g. run displays on jeida-18 format when only 3 LVDS lanes are
available.

Add parsing of an optional data-mapping devicetree property, which also
touches up the bits per color to match the bus format.

Signed-off-by: Johannes Zink <j.zink@pengutronix.de>
Link: https://lore.kernel.org/r/20230523-simplepanel_support_nondefault_datamapping-v5-3-0d7928edafab@pengutronix.de
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230523-simplepanel_support_nondefault_datamapping-v5-3-0d7928edafab@pengutronix.de

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index bb89e6d047bcb135c46f061348ff236388e0ab80..de0b84599e53336e011f0af12ab5a1fa5bc0aca2 100644 (file)
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -40,6 +40,7 @@
 #include <drm/drm_edid.h>
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_panel.h>
+#include <drm/drm_of.h>
 
 /**
  * struct panel_desc - Describes a simple panel.
@@ -549,6 +550,51 @@ static void panel_simple_parse_panel_timing_node(struct device *dev,
                dev_err(dev, "Reject override mode: No display_timing found\n");
 }
 
+static int panel_simple_override_nondefault_lvds_datamapping(struct device *dev,
+                                                            struct panel_simple *panel)
+{
+       int ret, bpc;
+
+       ret = drm_of_lvds_get_data_mapping(dev->of_node);
+       if (ret < 0) {
+               if (ret == -EINVAL)
+                       dev_warn(dev, "Ignore invalid data-mapping property\n");
+
+               /*
+                * Ignore non-existing or malformatted property, fallback to
+                * default data-mapping, and return 0.
+                */
+               return 0;
+       }
+
+       switch (ret) {
+       default:
+               WARN_ON(1);
+               fallthrough;
+       case MEDIA_BUS_FMT_RGB888_1X7X4_SPWG:
+               fallthrough;
+       case MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA:
+               bpc = 8;
+               break;
+       case MEDIA_BUS_FMT_RGB666_1X7X3_SPWG:
+               bpc = 6;
+       }
+
+       if (panel->desc->bpc != bpc || panel->desc->bus_format != ret) {
+               struct panel_desc *override_desc;
+
+               override_desc = devm_kmemdup(dev, panel->desc, sizeof(*panel->desc), GFP_KERNEL);
+               if (!override_desc)
+                       return -ENOMEM;
+
+               override_desc->bus_format = ret;
+               override_desc->bpc = bpc;
+               panel->desc = override_desc;
+       }
+
+       return 0;
+}
+
 static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 {
        struct panel_simple *panel;
@@ -601,6 +647,13 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
                        panel_simple_parse_panel_timing_node(dev, panel, &dt);
        }
 
+       if (desc->connector_type == DRM_MODE_CONNECTOR_LVDS) {
+               /* Optional data-mapping property for overriding bus format */
+               err = panel_simple_override_nondefault_lvds_datamapping(dev, panel);
+               if (err)
+                       goto free_ddc;
+       }
+
        connector_type = desc->connector_type;
        /* Catch common mistakes for panels. */
        switch (connector_type) {