linux-kernel - [PATCH v2 3/3] drm/panel-simple: allow LVDS format override

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Message-Id: <20230523-simplepanel_support_nondefault_datamapping-v2-3-87196f0d0b64@pengutronix.de>
Date:   Tue, 23 May 2023 10:19:43 +0200
From:   Johannes Zink <j.zink@...gutronix.de>
To:     David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>
Cc:     kernel test robot <lkp@...el.com>,
        Dan Carpenter <error27@...il.com>,
        patchwork-jzi@...gutronix.de, kernel@...gutronix.de,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johannes Zink <j.zink@...gutronix.de>
Subject: [PATCH v2 3/3] 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@...gutronix.de>

---

Changes:

  v1 -> v2: - fix missing unwind goto found by test robot
              Reported-by: kernel test robot <lkp@...el.com>
              Reported-by: Dan Carpenter <error27@...il.com>
              Link: https://lore.kernel.org/r/202304160359.4LHmFOlU-lkp@intel.com/
---
 drivers/gpu/drm/panel/panel-simple.c | 39 +++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 2a9c1a785a5c..0a35fdb49ccb 100644
--- 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.
@@ -559,7 +560,7 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 	struct device_node *ddc;
 	int connector_type;
 	u32 bus_flags;
-	int err;
+	int err, ret;
 
 	panel = devm_kzalloc(dev, sizeof(*panel), GFP_KERNEL);
 	if (!panel)
@@ -605,6 +606,42 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 			panel_simple_parse_panel_timing_node(dev, panel, &dt);
 	}
 
+
+	/* optional data-mapping property for overriding bus format */
+	ret = drm_of_lvds_get_data_mapping(dev->of_node);
+	if (ret == -EINVAL) {
+		dev_warn(dev, "Ignore invalid data-mapping property");
+	} else if (ret != -ENODEV) {
+		int bpc;
+
+		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 (desc->bpc != bpc || desc->bus_format != ret) {
+			struct panel_desc *override_desc;
+
+			override_desc = devm_kmemdup(dev, desc, sizeof(*desc), GFP_KERNEL);
+			if (!override_desc) {
+				err = -ENOMEM;
+				goto free_ddc;
+			}
+
+			override_desc->bus_format = ret;
+			override_desc->bpc = bpc;
+			panel->desc = override_desc;
+		}
+	}
+
 	connector_type = desc->connector_type;
 	/* Catch common mistakes for panels. */
 	switch (connector_type) {

-- 
2.39.2