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

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Message-ID: <CADnq5_OZiTtWLMS-hh56c8KZj1eEHQGVKh6pah-qct74e4Nabw@mail.gmail.com>
Date:   Wed, 23 Aug 2023 16:51:31 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Christian König <christian.koenig@....com>,
        "Mahfooz, Hamza" <Hamza.Mahfooz@....com>
Cc:     amd-gfx@...ts.freedesktop.org,
        Srinivasan Shanmugam <srinivasan.shanmugam@....com>,
        Guchun Chen <guchun.chen@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        stable@...r.kernel.org, Thomas Zimmermann <tzimmermann@...e.de>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v2] drm/amdgpu: register a dirty framebuffer callback for fbcon

@Mahfooz, Hamza
 can you respin with the NULL check?

Alex

On Wed, Aug 16, 2023 at 10:25 AM Christian König
<christian.koenig@....com> wrote:
>
> 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@....com>
> >>> Cc: Mario Limonciello <mario.limonciello@....com>
> >>> Cc: stable@...r.kernel.org # 6.1+
> >>> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2519
> >>> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
> >>> ---
> >>> 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@...e.de> 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;
> >>
>