[U-Boot] [PATCH 2/2] video: tegra: refuse to bind to disabled dcs

[Stephen Warren]

From: Stephen Warren <swarren at nvidia.com>

This prevents the following boot-time message on any board where only the
first DC is in use, yet the DC's DT node is enabled:

stdio_add_devices: Video device failed (ret=-22)

(This happens on at least Harmony, Ventana, and likely any other Tegra20
board with display enabled other than Seaboard).

The Tegra DC's DT node represents a display controller. It may itself
drive an integrated RGB display output, or be used by some other display
controller such as HDMI. For this reason the DC node itself is not
enabled/disabled in DT; the DC itself is considered a shared resource, not
the final (board-specific) display output. The node should instantiate a
display output driver only if the rgb subnode is enabled. Other output
drivers are free to use the DC if they are enabled and their DT node
references the DC's DT node. Adapt the Tegra display drivers' bind()
routine to only bind to the DC's DT node if the RGB subnode is enabled.

Now that the display driver does the right thing, remove the workaround
for this issue from Seaboard's DT file.

Cc: Thierry Reding <treding at nvidia.com>
Signed-off-by: Stephen Warren <swarren at nvidia.com>
---
Thierry, I assume this is how the DC nodes are intended to be interpreted?
It's certainly how the kernel's DT files and driver work, even if by
accident.
---
 arch/arm/dts/tegra20-seaboard.dts | 4 ----
 drivers/video/tegra.c             | 7 +++++++
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/arm/dts/tegra20-seaboard.dts b/arch/arm/dts/tegra20-seaboard.dts
index eada59073efc..5893d2a3f84e 100644
--- a/arch/arm/dts/tegra20-seaboard.dts
+++ b/arch/arm/dts/tegra20-seaboard.dts
@@ -40,10 +40,6 @@
 				nvidia,panel = <&lcd_panel>;
 			};
 		};
-
-		dc at 54240000 {
-			status = "disabled";
-		};
 	};
 
 	/* This is not used in U-Boot, but is expected to be in kernel .dts */
diff --git a/drivers/video/tegra.c b/drivers/video/tegra.c
index 7fd10e6af35e..c01809e89e14 100644
--- a/drivers/video/tegra.c
+++ b/drivers/video/tegra.c
@@ -620,6 +620,13 @@ static int tegra_lcd_ofdata_to_platdata(struct udevice *dev)
 static int tegra_lcd_bind(struct udevice *dev)
 {
 	struct video_uc_platdata *plat = dev_get_uclass_platdata(dev);
+	const void *blob = gd->fdt_blob;
+	int node = dev->of_offset;
+	int rgb;
+
+	rgb = fdt_subnode_offset(blob, node, "rgb");
+	if ((rgb < 0) || !fdtdec_get_is_enabled(blob, rgb))
+		return -ENODEV;
 
 	plat->size = LCD_MAX_WIDTH * LCD_MAX_HEIGHT *
 		(1 << LCD_MAX_LOG2_BPP) / 8;
-- 
2.8.1