drm/meson: fix colour distortion from HDR set during vendor u-boot

Add support for the OSD1 HDR registers so meson DRM can handle the HDR
properties set by Amlogic u-boot on G12A and newer devices which result
in blue/green/pink colour distortion to display output.

This takes the original patch submissions from Mathias [0] and [1] with
corrections for formatting and the missing description and attribution
needed for merge.

[0] https://lore.kernel.org/linux-amlogic/59dfd7e6-fc91-3d61-04c4-94e078a3188c@baylibre.com/T/
[1] https://lore.kernel.org/linux-amlogic/CAOKfEHBx_fboUqkENEMd-OC-NSrf46nto+vDLgvgttzPe99kXg@mail.gmail.com/T/#u

Fixes: 72888394 ("drm/meson: Add G12A Support for VIU setup")
Suggested-by: Mathias Steiger <mathias.steiger@googlemail.com>
Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Philip Milev <milev.philip@gmail.com>
[narmsrong: adding missing space on second tested-by tag]
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210806094005.7136-1-christianshewitt@gmail.com

drivers/gpu/drm/meson/meson_registers.h

@@ -634,6 +634,11 @@
 #define VPP_WRAP_OSD3_MATRIX_PRE_OFFSET2 0x3dbc
 #define VPP_WRAP_OSD3_MATRIX_EN_CTRL 0x3dbd
 
+/* osd1 HDR */
+#define OSD1_HDR2_CTRL 0x38a0
+#define OSD1_HDR2_CTRL_VDIN0_HDR2_TOP_EN       BIT(13)
+#define OSD1_HDR2_CTRL_REG_ONLY_MAT            BIT(16)
+
 /* osd2 scaler */
 #define OSD2_VSC_PHASE_STEP 0x3d00
 #define OSD2_VSC_INI_PHASE 0x3d01

drivers/gpu/drm/meson/meson_viu.c

@@ -425,9 +425,14 @@ void meson_viu_init(struct meson_drm *priv)
 	if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_GXM) ||
 	    meson_vpu_is_compatible(priv, VPU_COMPATIBLE_GXL))
 		meson_viu_load_matrix(priv);
-	else if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_G12A))
+	else if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_G12A)) {
 		meson_viu_set_g12a_osd1_matrix(priv, RGB709_to_YUV709l_coeff,
 					       true);
+		/* fix green/pink color distortion from vendor u-boot */
+		writel_bits_relaxed(OSD1_HDR2_CTRL_REG_ONLY_MAT |
+				OSD1_HDR2_CTRL_VDIN0_HDR2_TOP_EN, 0,
+				priv->io_base + _REG(OSD1_HDR2_CTRL));
+	}
 
 	/* Initialize OSD1 fifo control register */
 	reg = VIU_OSD_DDR_PRIORITY_URGENT |