mxsfb/nwl/panels: media bus format fixes

Components further up in the chain might ask us for supported formats.

Without this MEDIA_BUS_FMT_FIXED is assumed which then breaks display output with mxsfb since it can't determine a proper bus format.

We handle the bus formats that correspond to the DSI formats the bridge can potentially output (see chapter 13.6 of the i.MX 8MQ reference manual) - which matches what xsfb can input.

Fixes b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present")

Signed-off-by Guido Günther <[email protected]>

---
 drivers/gpu/drm/bridge/nwl-dsi.c | 35 ++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

drivers/gpu/drm/bridge/nwl-dsi.c +35 -0

index a251cc1f088f..27c80d36846b 100644
@@ -1234,6 +1234,40 @@ static void nwl_dsi_bridge_detach(struct drm_bridge *bridge)
 	drm_of_panel_bridge_remove(dsi->dev->of_node, 1, 0);
 }
 
+static u32 *nwl_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
+						 struct drm_bridge_state *bridge_state,
+						 struct drm_crtc_state *crtc_state,
+						 struct drm_connector_state *conn_state,
+						 u32 output_fmt,
+						 unsigned int *num_input_fmts)
+{
+	u32 *input_fmts, input_fmt;
+
+	*num_input_fmts = 0;
+
+	switch (output_fmt) {
+	/* If MEDIA_BUS_FMT_FIXED is tested, return default bus format */
+	case MEDIA_BUS_FMT_FIXED:
+		input_fmt = MEDIA_BUS_FMT_RGB888_1X24;
+		break;
+	case MEDIA_BUS_FMT_RGB888_1X24:
+	case MEDIA_BUS_FMT_RGB666_1X18:
+	case MEDIA_BUS_FMT_RGB565_1X16:
+		input_fmt = output_fmt;
+		break;
+	default:
+		return NULL;
+	}
+
+	input_fmts = kcalloc(1, sizeof(*input_fmts), GFP_KERNEL);
+	if (!input_fmts)
+		return NULL;
+	input_fmts[0] = input_fmt;
+	*num_input_fmts = 1;
+
+	return input_fmts;
+}
+
 static const struct drm_bridge_funcs nwl_dsi_bridge_funcs = {
 	.atomic_duplicate_state	= drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state	= drm_atomic_helper_bridge_destroy_state,

@@ -1241,6 +1275,7 @@ static const struct drm_bridge_funcs nwl_dsi_bridge_funcs = {
 	.atomic_check		= nwl_dsi_bridge_atomic_check,
 	.atomic_enable		= nwl_dsi_bridge_atomic_enable,
 	.atomic_disable		= nwl_dsi_bridge_atomic_disable,
+	.atomic_get_input_bus_fmts = nwl_bridge_atomic_get_input_bus_fmts,
 	.mode_set		= nwl_dsi_bridge_mode_set,
 	.mode_valid		= nwl_dsi_bridge_mode_valid,
 	.attach			= nwl_dsi_bridge_attach,

media-bus-formats.h has them in hexadecimal as well so matching with that file saves one conversion when debugging.

Signed-off-by Guido Günther <[email protected]>

---
 drivers/gpu/drm/mxsfb/mxsfb_kms.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/gpu/drm/mxsfb/mxsfb_kms.c +1 -1

index af6c620adf6e..d6abd2077114 100644
@@ -89,7 +89,7 @@ static void mxsfb_set_formats(struct mxsfb_drm_private *mxsfb,
 		ctrl |= CTRL_BUS_WIDTH_24;
 		break;
 	default:
-		dev_err(drm->dev, "Unknown media bus format %d\n", bus_format);
+		dev_err(drm->dev, "Unknown media bus format 0x%x\n", bus_format);
 		break;
 	}
 

If a bridge doesn't do any bus format handling MEDIA_BUS_FMT_FIXED is returned. Fallback to a reasonable default (MEDIA_BUS_FMT_RGB888_1X24) in that case.

This unbreaks e.g. using mxsfb with the nwl bridge and mipi panels.

Fixes b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present")

Reported-by Martin Kepplinger <[email protected]>

Signed-off-by Guido Günther <[email protected]>

---
 drivers/gpu/drm/mxsfb/mxsfb_kms.c | 6 ++++++
 1 file changed, 6 insertions(+)

drivers/gpu/drm/mxsfb/mxsfb_kms.c +6 -0

index d6abd2077114..e3fbb8b58d5d 100644
@@ -369,6 +369,12 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,
 			drm_atomic_get_new_bridge_state(state,
 							mxsfb->bridge);
 		bus_format = bridge_state->input_bus_cfg.format;
+		if (bus_format == MEDIA_BUS_FMT_FIXED) {
+			dev_warn_once(drm->dev,
+				      "Bridge does not provide bus format, assuming MEDIA_BUS_FMT_RGB888_1X24.\n"
+				      "Please fix bridge driver by handling atomic_get_input_bus_fmts.\n");
+			bus_format = MEDIA_BUS_FMT_RGB888_1X24;
+		}
 	}
 
 	/* If there is no bridge, use bus format from connector */

Am Montag, dem 04.10.2021 um 09:27 +0200 schrieb Guido Günther:

Quoted 4 lines

If a bridge doesn't do any bus format handling MEDIA_BUS_FMT_FIXED is returned. Fallback to a reasonable default (MEDIA_BUS_FMT_RGB888_1X24) in that case.

Quoted 4 lines

This unbreaks e.g. using mxsfb with the nwl bridge and mipi panels.

Fixes b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present")

I don't think this qualifies for stable, so I would drop this tag, as the stable maintainers are quite trigger happy to pull in patches with a fixes tag. Also the subject isn't quite correct, this isn't setting a "proper" bus format, but rather adds a fallback. Other than that:

Reviewed-by Lucas Stach <[email protected]>

Regards,
Lucas

Quoted 24 lines

Reported-by Martin Kepplinger <[email protected]>

Signed-off-by Guido Günther <[email protected]>

---
 drivers/gpu/drm/mxsfb/mxsfb_kms.c | 6 ++++++
 1 file changed, 6 insertions(+)

drivers/gpu/drm/mxsfb/mxsfb_kms.c +6 -0

index d6abd2077114..e3fbb8b58d5d 100644
@@ -369,6 +369,12 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,
 			drm_atomic_get_new_bridge_state(state,
 							mxsfb->bridge);
 		bus_format = bridge_state->input_bus_cfg.format;
+		if (bus_format == MEDIA_BUS_FMT_FIXED) {
+			dev_warn_once(drm->dev,
+				      "Bridge does not provide bus format, assuming MEDIA_BUS_FMT_RGB888_1X24.\n"
+				      "Please fix bridge driver by handling atomic_get_input_bus_fmts.\n");
+			bus_format = MEDIA_BUS_FMT_RGB888_1X24;
+		}
 	}
 
 	/* If there is no bridge, use bus format from connector */