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/[e-mail]/T/
[1] https://lore.kernel.org/linux-amlogic/[e-mail]/T/#u

Fixes: 728883948b0d ("drm/meson: Add G12A Support for VIU setup")
Suggested-by: Mathias Steiger <[e-mail]>
Signed-off-by: Christian Hewitt <[e-mail]>
Tested-by: Neil Armstrong <[e-mail]>
Tested-by: Philip Milev <[e-mail]>
[narmsrong: adding missing space on second tested-by tag]
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/meson/meson_registers.h

···
 #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

···
 	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 |