[Intel-gfx] [PATCH] drm/i915/fbdev: Enable late fbdev initial configuration

[Souza, Jose]

On Wed, 2018-04-18 at 00:44 +0100, Chris Wilson wrote:
> Quoting José Roberto de Souza (2018-04-17 23:34:18)
> > If the initial fbdev configuration(intel_fbdev_initial_config())
> > runs and
> > there still no sink connected it will cause
> > drm_fb_helper_initial_config() to return 0 as no error happened(but
> > internally the return is -EAGAIN).
> > Because no framebuffer was allocated, when a sink is connected
> > intel_fbdev_output_poll_changed() will not execute
> > drm_fb_helper_hotplug_event() that would trigger another try to do
> > the
> > initial fbdev configuration.
> > 
> > So here creating a dummy framebuffer of 800x600, so
> > drm_fb_helper_hotplug_event() will be executed and fbdev can be
> > properly
> > setup when a sink is connected, if needed the dummy framebuffer
> > will be
> > freed and a new with the proper size will be allocated.
> > 
> > This issue also happens when a MST DP sink is connected since boot,
> > as
> > the MST topology is discovered in parallel if
> > intel_fbdev_initial_config()
> > is executed before the first sink MST is discovered it will cause
> > this
> > same issue.
> > 
> > This is a follow up patch of
> > https://patchwork.freedesktop.org/patch/196089/
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104158
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104425
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_fbdev.c | 24 +++++++++++++++++++++++-
> >  1 file changed, 23 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_fbdev.c
> > b/drivers/gpu/drm/i915/intel_fbdev.c
> > index 7d41d139341b..773577d39782 100644
> > --- a/drivers/gpu/drm/i915/intel_fbdev.c
> > +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> > @@ -696,14 +696,36 @@ int intel_fbdev_init(struct drm_device *dev)
> >         return 0;
> >  }
> >  
> > +static void intel_fbdev_dummy_fb_create(struct intel_fbdev
> > *ifbdev)
> > +{
> > +       struct drm_fb_helper_surface_size sizes;
> > +
> > +       sizes.fb_width = 800;
> > +       sizes.fb_height = 600;
> > +       sizes.surface_width = sizes.fb_width;
> > +       sizes.surface_height = sizes.fb_height;
> > +       sizes.surface_bpp = 32;
> > +       sizes.surface_depth = 24;
> > +
> > +       if (intelfb_create(&ifbdev->helper, &sizes))
> > +               DRM_ERROR("Unable to create dummy framebufer");
> > +}
> > +
> >  static void intel_fbdev_initial_config(void *data, async_cookie_t
> > cookie)
> >  {
> >         struct intel_fbdev *ifbdev = data;
> >  
> >         /* Due to peculiar init order wrt to hpd handling this is
> > separate. */
> >         if (drm_fb_helper_initial_config(&ifbdev->helper,
> > -                                        ifbdev->preferred_bpp))
> > +                                        ifbdev->preferred_bpp)) {
> >                 intel_fbdev_unregister(to_i915(ifbdev-
> > >helper.dev));
> > +               return;
> > +       }
> > +
> > +       mutex_lock(&ifbdev->helper.lock);
> > +       if (!ifbdev->vma)
> > +               intel_fbdev_dummy_fb_create(ifbdev);
> > +       mutex_unlock(&ifbdev->helper.lock);
> >  }
> 
> Did you try
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c
> b/drivers/gpu/drm/i915/intel_fbdev.c
> index 65a3313723c9..4120c635742d 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -493,6 +493,7 @@ static bool intel_fb_initial_config(struct
> drm_fb_helper *fb_helper,
>  bail:
>                 DRM_DEBUG_KMS("Not using firmware configuration\n");
>                 memcpy(enabled, save_enabled, count);
> +               fb_helper->deferred_setup = true;

This is too earlier to set deferred_setup when
intel_fb_initial_config() fails,
__drm_fb_helper_initial_config_and_unlock() will then try to
probe/create a fb but as there is no sink connected it will fail too.

Also __drm_fb_helper_initial_config_and_unlock() is already setting
deferred_setup if both attempts fails.

>                 ret = false;
>         }
> 
> possible as of 
> 
> commit ca91a2758fcef6635626993557dd51cfbb6dd134
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date:   Thu Jul 6 15:00:21 2017 +0200
> 
>     drm/fb-helper: Support deferred setup
>     
>     FB helper code falls back to a 1024x768 mode if no outputs are
> connected
>     or don't report back any modes upon initialization. This can be
> annoying
>     because outputs that are added to FB helper later on can't be
> used with
>     FB helper if they don't support a matching mode.
>     ...
> 
> -Chris
>