Re: [PATCH] drm/virtgpu: Add PM support for suspend/resume

["Morris Pan (潘泰為)" <Morris.Pan@mediatek.com>]

On Wed, 2026-04-01 at 08:24 +0200, Thomas Zimmermann wrote:
> 
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> 
> 
> Hi
> 
> Am 01.04.26 um 08:10 schrieb Morris Pan:
> > Add freeze/restore callbacks to handle system suspend/resume.
> > During freeze, delete virtqueues and reset device.
> > During restore, reinitialize virtqueues and mark device ready.
> > 
> > Signed-off-by: Morris Pan <morris.pan@mediatek.com>
> > ---
> >   drivers/gpu/drm/virtio/virtgpu_drv.c | 40
> > +++++++++++++++++++++++++++-
> >   1 file changed, 39 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c
> > b/drivers/gpu/drm/virtio/virtgpu_drv.c
> > index a5ce96fb8a1d..fbca0a82958c 100644
> > --- a/drivers/gpu/drm/virtio/virtgpu_drv.c
> > +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
> > @@ -145,6 +145,40 @@ static void virtio_gpu_config_changed(struct
> > virtio_device *vdev)
> >       schedule_work(&vgdev->config_changed_work);
> >   }
> > 
> > +#ifdef CONFIG_PM_SLEEP
> > +static int virtgpu_freeze(struct virtio_device *vdev)
> > +{
> 
> I think you first need to call drm_mode_config_helper_suspend() [1]
> to
> stop DRM and save the current state.
> 
> [1]
> https://urldefense.com/v3/__https://elixir.bootlin.com/linux/v6.19.10/source/drivers/gpu/drm/drm_modeset_helper.c*L179__;Iw!!CTRNKA9wMg0ARbw!j0dxkuooYYkTXqgRzLyo558VesWoTL84VgkwhRczVxZ-PZlBeLg0vnY4B36rtYVRDVpGmTqVjGKJoFh7KnVelak$
> 
> > +     vdev->config->del_vqs(vdev);
> > +     virtio_reset_device(vdev);
> > +
> > +     return 0;
> > +}
> > +
> > +static int virtgpu_restore(struct virtio_device *vdev)
> > +{
> > +     int ret;
> > +     struct virtqueue *vqs[2];
> > +     struct drm_device *dev = vdev->priv;
> > +     struct virtio_gpu_device *vgdev = dev->dev_private;
> > +     struct virtqueue_info vqs_info[] = {
> > +             { "control", virtio_gpu_ctrl_ack },
> > +             { "cursor", virtio_gpu_cursor_ack },
> > +     };
> > +
> > +     ret = virtio_find_vqs(vdev, 2, vqs, vqs_info, NULL);
> > +     if (ret) {
> > +             DRM_ERROR("failed to find virtio queues\n");
> > +             return ret;
> > +     }
> > +
> > +     vgdev->ctrlq.vq = vqs[0];
> > +     vgdev->cursorq.vq = vqs[1];
> > +     virtio_device_ready(vdev);
> 
> And here you have to call drm_mode_config_helper_resume() [2] to
> restore
> the DRM state from before the freeze.
> 
> [2]
> https://urldefense.com/v3/__https://elixir.bootlin.com/linux/v6.19.10/source/drivers/gpu/drm/drm_modeset_helper.c*L227__;Iw!!CTRNKA9wMg0ARbw!j0dxkuooYYkTXqgRzLyo558VesWoTL84VgkwhRczVxZ-PZlBeLg0vnY4B36rtYVRDVpGmTqVjGKJoFh7cv1EDgQ$
> 
> Best regards
> Thomas
> 
> > +
> > +     return 0;
> > +}
> > +#endif
> > +
> >   static struct virtio_device_id id_table[] = {
> >       { VIRTIO_ID_GPU, VIRTIO_DEV_ANY_ID },
> >       { 0 },
> > @@ -172,7 +206,11 @@ static struct virtio_driver virtio_gpu_driver
> > = {
> >       .probe = virtio_gpu_probe,
> >       .remove = virtio_gpu_remove,
> >       .shutdown = virtio_gpu_shutdown,
> > -     .config_changed = virtio_gpu_config_changed
> > +     .config_changed = virtio_gpu_config_changed,
> > +#ifdef CONFIG_PM_SLEEP
> > +     .freeze = virtgpu_freeze,
> > +     .restore = virtgpu_restore
> > +#endif
> >   };
> > 
> >   static int __init virtio_gpu_driver_init(void)
> 
> --
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Frankenstr. 146, 90461 Nürnberg, Germany,
> https://urldefense.com/v3/__http://www.suse.com__;!!CTRNKA9wMg0ARbw!j0dxkuooYYkTXqgRzLyo558VesWoTL84VgkwhRczVxZ-PZlBeLg0vnY4B36rtYVRDVpGmTqVjGKJoFh74dj3x1M$
> GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG
> Nürnberg)
> 
> 

Hi Thomas,

Thank you very much for your detailed review and the constructive
feedback on my patch.

I am currently working on the revisions based on your comments.

Thanks again for your time and guidance.

Best regards,
Morris