Re: [PATCH] drm/panel: Add prepare_prev_first flag to Visionox VTDR6130

[Jessica Zhang]

On 7/31/2023 6:00 AM, Neil Armstrong wrote:
> Hi,
>
> On 26/07/2023 00:56, Jessica Zhang wrote:
> > Due to a recent introduction of the pre_enable_prev_first bridge flag 
> > [1],
> > the panel driver will be probed before the DSI is enabled, causing the
> > DCS commands to fail to send.
> >
> > Ensure that DSI is enabled before panel probe by setting the
> > prepare_prev_first flag for the panel.
>
> Well this is specific to MSM DSI driver, it's not related at all to the 
> panel.

Hi Neil,

I think there might be some confusion caused by the commit message -- 
instead of "enabled before panel probe", it should be "enabled before 
panel pre_enable()" as the panel on commands are sent during prepare(), 
which is matched to bridge pre_enable().

IIRC the general rule is that the panel driver should set the 
prepare_prev_first flag if the on commands are sent during pre_enable(), 
so I'll keep the code change but correct the commit message if that's ok 
with you.

Thanks,

Jessica Zhang

> Neil
>
> > [1] commit 4fb912e5e190 ("drm/bridge: Introduce pre_enable_prev_first 
> > to alter bridge init order")
> >
> > Fixes: 2349183d32d8 ("drm/panel: add visionox vtdr6130 DSI panel driver")
> > Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/panel/panel-visionox-vtdr6130.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c 
> > b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
> > index bb0dfd86ea67..e1363e128e7e 100644
> > --- a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
> > +++ b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
> > @@ -296,6 +296,7 @@ static int visionox_vtdr6130_probe(struct 
> > mipi_dsi_device *dsi)
> >       dsi->format = MIPI_DSI_FMT_RGB888;
> >       dsi->mode_flags = MIPI_DSI_MODE_VIDEO | 
> > MIPI_DSI_MODE_NO_EOT_PACKET |
> >                 MIPI_DSI_CLOCK_NON_CONTINUOUS;
> > +    ctx->panel.prepare_prev_first = true;
> >       drm_panel_init(&ctx->panel, dev, &visionox_vtdr6130_panel_funcs,
> >                  DRM_MODE_CONNECTOR_DSI);
> >
> > ---
> > base-commit: 28a5c036b05fc5c935cc72d76abd3589825ea9cd
> > change-id: 20230717-visionox-vtdr-prev-first-e00ae02eec9f
> >
> > Best regards,