Re: [PATCH v2] drm/amdgpu: register a dirty framebuffer callback for fbcon

[Christian König]

Am 16.08.23 um 15:41 schrieb Hamza Mahfooz:
> On 8/16/23 01:55, Christian König wrote:
> > Am 15.08.23 um 19:26 schrieb Hamza Mahfooz:
> > > fbcon requires that we implement &drm_framebuffer_funcs.dirty.
> > > Otherwise, the framebuffer might take a while to flush (which would
> > > manifest as noticeable lag). However, we can't enable this callback for
> > > non-fbcon cases since it might cause too many atomic commits to be made
> > > at once. So, implement amdgpu_dirtyfb() and only enable it for fbcon
> > > framebuffers on devices that support atomic KMS.
> > >
> > > Cc: Aurabindo Pillai <aurabindo.pillai@xxxxxxx>
> > > Cc: Mario Limonciello <mario.limonciello@xxxxxxx>
> > > Cc: stable@xxxxxxxxxxxxxxx # 6.1+
> > > Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2519
> > > Signed-off-by: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
> > > ---
> > > v2: update variable names
> > > ---
> > >   drivers/gpu/drm/amd/amdgpu/amdgpu_display.c | 26 
> > > ++++++++++++++++++++-
> > >   1 file changed, 25 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c 
> > > b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> > > index d20dd3f852fc..d3b59f99cb7c 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_display.c
> > > @@ -38,6 +38,8 @@
> > >   #include <linux/pci.h>
> > >   #include <linux/pm_runtime.h>
> > >   #include <drm/drm_crtc_helper.h>
> > > +#include <drm/drm_damage_helper.h>
> > > +#include <drm/drm_drv.h>
> > >   #include <drm/drm_edid.h>
> > >   #include <drm/drm_fb_helper.h>
> > >   #include <drm/drm_gem_framebuffer_helper.h>
> > > @@ -532,11 +534,29 @@ bool amdgpu_display_ddc_probe(struct 
> > > amdgpu_connector *amdgpu_connector,
> > >       return true;
> > >   }
> > > +static int amdgpu_dirtyfb(struct drm_framebuffer *fb, struct 
> > > drm_file *file,
> > > +              unsigned int flags, unsigned int color,
> > > +              struct drm_clip_rect *clips, unsigned int num_clips)
> > > +{
> > > +
> > > +    if (strcmp(fb->comm, "[fbcon]"))
> > > +        return -ENOSYS;
> >
> > Once more to the v2 of this patch: Tests like those are a pretty big 
> > NO-GO for upstreaming.
>
> On closer inspection it is actually sufficient to check if `file` is
> NULL here (since it means that the request isn't from userspace). So, do
> you think that would be palatable for upstream?

That's certainly better than doing a string compare, but I'm not sure if 
that's sufficient.

In general drivers shouldn't have any special handling for fdcon.

You should probably have Thomas Zimmermann <tzimmermann@xxxxxxx> take a 
look at this.

Regards,
Christian.

> > Regards,
> > Christian.
> >
> > > +
> > > +    return drm_atomic_helper_dirtyfb(fb, file, flags, color, clips,
> > > +                     num_clips);
> > > +}
> > > +
> > >   static const struct drm_framebuffer_funcs amdgpu_fb_funcs = {
> > >       .destroy = drm_gem_fb_destroy,
> > >       .create_handle = drm_gem_fb_create_handle,
> > >   };
> > > +static const struct drm_framebuffer_funcs amdgpu_fb_funcs_atomic = {
> > > +    .destroy = drm_gem_fb_destroy,
> > > +    .create_handle = drm_gem_fb_create_handle,
> > > +    .dirty = amdgpu_dirtyfb
> > > +};
> > > +
> > >   uint32_t amdgpu_display_supported_domains(struct amdgpu_device *adev,
> > >                         uint64_t bo_flags)
> > >   {
> > > @@ -1139,7 +1159,11 @@ static int 
> > > amdgpu_display_gem_fb_verify_and_init(struct drm_device *dev,
> > >       if (ret)
> > >           goto err;
> > > -    ret = drm_framebuffer_init(dev, &rfb->base, &amdgpu_fb_funcs);
> > > +    if (drm_drv_uses_atomic_modeset(dev))
> > > +        ret = drm_framebuffer_init(dev, &rfb->base,
> > > +                       &amdgpu_fb_funcs_atomic);
> > > +    else
> > > +        ret = drm_framebuffer_init(dev, &rfb->base, &amdgpu_fb_funcs);
> > >       if (ret)
> > >           goto err;