openwrt/target/linux/bcm27xx/patches-5.15/950-0431-drm-vc4-Change-the-default-DPI-format-to-being-18bpp.patch

From bf6ce41170822705037cc070b89a85ac4e6a4645 Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Fri, 12 Feb 2021 17:31:37 +0000
Subject: [PATCH] drm/vc4: Change the default DPI format to being
 18bpp, not 24.

DPI hasn't really been used up until now, so the default has
been meaningless.
In theory we should be able to pass the desired format for the
adjacent bridge chip through, but framework seems to be missing
for that.

As the main device to use DPI is the VGA666 or Adafruit Kippah,
both of which use RGB666, change the default to being RGB666 instead
of RGB888.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
 drivers/gpu/drm/vc4/vc4_dpi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/vc4/vc4_dpi.c
+++ b/drivers/gpu/drm/vc4/vc4_dpi.c
@@ -198,8 +198,8 @@ static void vc4_dpi_encoder_enable(struc
 		if (connector->display_info.bus_flags & DRM_BUS_FLAG_DE_LOW)
 			dpi_c |= DPI_OUTPUT_ENABLE_INVERT;
 	} else {
-		/* Default to 24bit if no connector found. */
-		dpi_c |= VC4_SET_FIELD(DPI_FORMAT_24BIT_888_RGB, DPI_FORMAT);
+		/* Default to 18bit if no connector found. */
+		dpi_c |= VC4_SET_FIELD(DPI_FORMAT_18BIT_666_RGB_1, DPI_FORMAT);
 	}
 
 	if (mode->flags & DRM_MODE_FLAG_NHSYNC)