On 9/28/21 11:27 AM, Lucas Stach wrote:
Am Dienstag, dem 28.09.2021 um 11:19 +0200 schrieb Guido Günther:
Hi,
On Tue, Sep 28, 2021 at 11:08:58AM +0200, Marek Vasut wrote:
On 9/28/21 10:55 AM, Guido Günther wrote:
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")
Signed-off-by: Guido Günther <agx@xxxxxxxxxxx>
---
I'll look at what needs to be done in nwl separately but this also
unbreaks other bridge seupts that don't to format negotiation yet.
drivers/gpu/drm/mxsfb/mxsfb_kms.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
index af6c620adf6e..4ef94cf686b0 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
@@ -369,6 +369,8 @@ 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)
+ bus_format = MEDIA_BUS_FMT_RGB888_1X24;
Shouldn't the NWL bridge return the correct format ?
Yes it should and I'll send a separate patch for that but we currently
don't do anything meaningful at all if the bridge doesn't do format
negotiation and then fail setup in mxsfb_set_formats().
I think we should at least preserve the status quo (as we do with the
non bridge case in b776b0f00f24 too).
We could have a warning to spot drivers that don't do that yet and hence
the generic code returns MEDIA_BUS_FMT_FIXED.
That sounds sensible. Using a default format if we don't know what to
do is going to be a unpleasant surprise for those with a display
pipeline that doesn't work with the default format. So please add a
dev_warn when we are doing this fallback.
Also I would argue that the NWL fix is the patch that should go in the
stable tree. This one should only be a additional safety net, so I
would drop the Fixes tag.
Indeed
