Re: [PATCH 1/2] drm/nouveau: Disable atomic support on a per-device basis

[Lyude Paul <lyude@redhat.com>]

On Fri, 2018-09-14 at 10:11 +0200, Daniel Vetter wrote:
> On Thu, Sep 13, 2018 at 11:02 PM, Lyude Paul <lyude@redhat.com> wrote:
> > Hm, one nitpick here. Since /sys/kernel/debug/dri/*/state creation depends
> > on
> > the driver supporting atomic, maybe it would be good to make it so that we
> > set
> > DRIVER_ATOMIC in the driver_stub structure, then disable it per-device
> > depending
> > on the nouveau_atomic setting + hw support. That way we can always have the
> > state debugfs file while maintaining nouveau's current behavior with
> > exposing
> > atomic ioctls. Assuming that wouldn't have any unintended side-effects of
> > course
> 
> dri/*/state only works with atomic drivers. There's no explicit state
> with legacy drivers at all, it's all just implicit in hw and some
> random driver structures.
> 
> We should make sure though that the debugfs stuff looks at
> drm_drv_uses_atomic_modsetting(), and not DRIVER_ATOMIC. Former is
> about the internals (i915 is internally atomic everywhere), latter
> about the uapi (some old platforms aren't properly validated for full
> atomic features, hence why it's disabled).
> -Daniel
Makes sense, it seems doing that results in exactly what I wanted with nouveau!
As for this patch:

Reviewed-by: Lyude Paul <lyude@redhat.com>

> 
> > On Thu, 2018-09-13 at 19:31 +0300, Ville Syrjala wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > We now have per-device driver_features, so let's use that
> > > to disable atomic only for pre-nv50.
> > > 
> > > Cc: Ben Skeggs <bskeggs@redhat.com>
> > > Cc: Lyude Paul <lyude@redhat.com>
> > > Cc: nouveau@lists.freedesktop.org
> > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/nouveau/dispnv04/disp.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/nouveau/dispnv04/disp.c
> > > b/drivers/gpu/drm/nouveau/dispnv04/disp.c
> > > index 70dce544984e..670535a68d3b 100644
> > > --- a/drivers/gpu/drm/nouveau/dispnv04/disp.c
> > > +++ b/drivers/gpu/drm/nouveau/dispnv04/disp.c
> > > @@ -56,7 +56,7 @@ nv04_display_create(struct drm_device *dev)
> > >       nouveau_display(dev)->fini = nv04_display_fini;
> > > 
> > >       /* Pre-nv50 doesn't support atomic, so don't expose the ioctls */
> > > -     dev->driver->driver_features &= ~DRIVER_ATOMIC;
> > > +     dev->driver_features &= ~DRIVER_ATOMIC;
> > > 
> > >       nouveau_hw_save_vga_fonts(dev, 1);
> > > 
> 
> 
> 

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