Re: [PATCH] drm/ast: Fix default resolution when no monitor is connected on DP

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

(cc: some people from commit fae7d186403e)

Am 04.07.23 um 16:19 schrieb Thomas Zimmermann:
> Hi Jocelyn
>
> Am 23.06.23 um 11:46 schrieb Jocelyn Falempe:
> > Since commit fae7d186403e ("drm/probe-helper: Default to 640x480 if no
> >   EDID on DP")
> > The default resolution is now 640x480 when no monitor is connected.
> > But Aspeed graphics is mostly used in servers, where no monitor
> > is attached. This also affects the "remote" resolution to 640x480, 
> > which is
> > inconvenient, and breaks the anaconda installer.
>
> By "remote resolution", you mean the display mode that the BMC uses?
>
> > So when no EDID is present, set 1024x768 as preferred resolution.
> >
> > Fixes: fae7d186403e ("drm/probe-helper: Default to 640x480 if no EDID 
> > on DP")
>
> This commit says that 640x480 is the designated failsafe mode if no EDID 
> is available. Therefore, I think we should not override it 
> unconditionally. The ast driver is no special in that case.
>
> But I see why you're doing this change. I think any solution should be 
> implemented in drm_helper_probe_single_connector_modes().
>
> But before we solve this in the kernel, is it possible to delegate this 
> to userspace? If no EDID has been given, userspace could try a 
> non-failsafe display mode.
>
> Best regards
> Thomas
>
> > Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/ast/ast_mode.c | 26 ++++++++++++++++++++++++--
> >   1 file changed, 24 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ast/ast_mode.c 
> > b/drivers/gpu/drm/ast/ast_mode.c
> > index 36374828f6c8..8f7b7cc021c7 100644
> > --- a/drivers/gpu/drm/ast/ast_mode.c
> > +++ b/drivers/gpu/drm/ast/ast_mode.c
> > @@ -1589,9 +1589,31 @@ static const struct drm_connector_helper_funcs 
> > ast_dp501_connector_helper_funcs
> >       .get_modes = ast_dp501_connector_helper_get_modes,
> >   };
> > +static int ast_dp_probe_single_connector_modes(struct drm_connector 
> > *connector,
> > +                           uint32_t maxX, uint32_t maxY)
> > +{
> > +    int ret;
> > +    struct drm_display_mode *mode;
> > +
> > +    ret = drm_helper_probe_single_connector_modes(connector, maxX, 
> > maxY);
> > +    /*
> > +     * When no monitor are detected, DP now default to 640x480
> > +     * As aspeed is mostly used in remote server, and DP monitors are
> > +     * rarely attached, it's better to default to 1024x768
> > +     */
> > +    if (!connector->edid_blob_ptr) {
> > +        list_for_each_entry(mode, &connector->modes, head) {
> > +            if (mode->hdisplay == 1024 && mode->vdisplay == 768)
> > +                mode->type |= DRM_MODE_TYPE_PREFERRED;
> > +            drm_mode_sort(&connector->modes);
> > +        }
> > +    }
> > +    return ret;
> > +}
> > +
> >   static const struct drm_connector_funcs ast_dp501_connector_funcs = {
> >       .reset = drm_atomic_helper_connector_reset,
> > -    .fill_modes = drm_helper_probe_single_connector_modes,
> > +    .fill_modes = ast_dp_probe_single_connector_modes,
> >       .destroy = drm_connector_cleanup,
> >       .atomic_duplicate_state = 
> > drm_atomic_helper_connector_duplicate_state,
> >       .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> > @@ -1678,7 +1700,7 @@ static const struct drm_connector_helper_funcs 
> > ast_astdp_connector_helper_funcs
> >   static const struct drm_connector_funcs ast_astdp_connector_funcs = {
> >       .reset = drm_atomic_helper_connector_reset,
> > -    .fill_modes = drm_helper_probe_single_connector_modes,
> > +    .fill_modes = ast_dp_probe_single_connector_modes,
> >       .destroy = drm_connector_cleanup,
> >       .atomic_duplicate_state = 
> > drm_atomic_helper_connector_duplicate_state,
> >       .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> >
> > base-commit: 0adec22702d497385dbdc52abb165f379a00efba

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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