Re: [PATCH v2 1/3] gpu/drm: ingenic: Add trick to support 16bpp on 24-bit panels

From: Paul Cercueil
Date: Wed Apr 08 2020 - 05:52:02 EST


Hi,

Any feedback for this patchset?

Thanks,
-Paul


Le mer. 26 févr. 2020 à 1:30, Paul Cercueil <paul@xxxxxxxxxxxxxxx> a écrit :
If the panel interface is 24-bit but our primary plane is 16bpp,
configure as if the panel was 18-bit. This tricks permits the display
of 16bpp data on a 24-bit panel by wiring each color component to the
MSBs of the 24-bit interface.

v2: Check bytes-per-pixel count instead of fourcc format

Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/ingenic/ingenic-drm.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ingenic/ingenic-drm.c b/drivers/gpu/drm/ingenic/ingenic-drm.c
index 6d47ef7b148c..5493a80d7d2f 100644
--- a/drivers/gpu/drm/ingenic/ingenic-drm.c
+++ b/drivers/gpu/drm/ingenic/ingenic-drm.c
@@ -400,6 +400,8 @@ static void ingenic_drm_encoder_atomic_mode_set(struct drm_encoder *encoder,
struct drm_display_mode *mode = &crtc_state->adjusted_mode;
struct drm_connector *conn = conn_state->connector;
struct drm_display_info *info = &conn->display_info;
+ struct drm_plane_state *plane_state = crtc_state->crtc->primary->state;
+ const struct drm_format_info *finfo = NULL;
unsigned int cfg;

priv->panel_is_sharp = info->bus_flags & DRM_BUS_FLAG_SHARP_SIGNALS;
@@ -435,7 +437,21 @@ static void ingenic_drm_encoder_atomic_mode_set(struct drm_encoder *encoder,
cfg |= JZ_LCD_CFG_MODE_GENERIC_18BIT;
break;
case MEDIA_BUS_FMT_RGB888_1X24:
- cfg |= JZ_LCD_CFG_MODE_GENERIC_24BIT;
+ if (plane_state && plane_state->fb)
+ finfo = plane_state->fb->format;
+
+ /*
+ * If the panel interface is 24-bit but our
+ * primary plane is 16bpp, configure as if the
+ * panel was 18-bit. This tricks permits the
+ * display of 16bpp data on a 24-bit panel by
+ * wiring each color component to the MSBs of
+ * the 24-bit interface.
+ */
+ if (finfo && finfo->cpp[0] < 3)
+ cfg |= JZ_LCD_CFG_MODE_GENERIC_18BIT;
+ else
+ cfg |= JZ_LCD_CFG_MODE_GENERIC_24BIT;
break;
case MEDIA_BUS_FMT_RGB888_3X8:
cfg |= JZ_LCD_CFG_MODE_8BIT_SERIAL;
--
2.25.0