Re: [PATCH v2 1/9] drm: Do delayed switcheroo in drm_lastclose()

[Daniel Vetter <daniel.vetter@ffwll.ch>]

On Mon, Aug 12, 2024 at 10:28:22AM +0200, Thomas Zimmermann wrote:
> Amdgpu and nouveau call vga_switcheroo_process_delayed_switch() from
> their lastclose callbacks. Call it from drm_lastclose(), so that the
> driver functions can finally be removed. Only PCI devices with enabled
> switcheroo do the delayed switching. The call has no effect on other
> hardware.
> 
> v2:
> - move change to drm_lastclose() (Sima)
> - update docs for vga_switcheroo_process_delayed_switch()
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

A bit an aside: The entire vgaswitcheroo code is still a midlayer mess,
where the locking is at the wrong layers resulting in the can_switch check
potentially being racy. But that's a different can of worms.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/drm_file.c       | 4 ++++
>  drivers/gpu/vga/vga_switcheroo.c | 3 +--
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index 714e42b05108..513bef816ae9 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -38,6 +38,7 @@
>  #include <linux/pci.h>
>  #include <linux/poll.h>
>  #include <linux/slab.h>
> +#include <linux/vga_switcheroo.h>
>  
>  #include <drm/drm_client.h>
>  #include <drm/drm_drv.h>
> @@ -404,6 +405,9 @@ void drm_lastclose(struct drm_device * dev)
>  	drm_dbg_core(dev, "driver lastclose completed\n");
>  
>  	drm_client_dev_restore(dev);
> +
> +	if (dev_is_pci(dev->dev))
> +		vga_switcheroo_process_delayed_switch();
>  }
>  
>  /**
> diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
> index 365e6ddbe90f..18f2c92beff8 100644
> --- a/drivers/gpu/vga/vga_switcheroo.c
> +++ b/drivers/gpu/vga/vga_switcheroo.c
> @@ -926,8 +926,7 @@ static void vga_switcheroo_debugfs_init(struct vgasr_priv *priv)
>  /**
>   * vga_switcheroo_process_delayed_switch() - helper for delayed switching
>   *
> - * Process a delayed switch if one is pending. DRM drivers should call this
> - * from their ->lastclose callback.
> + * Process a delayed switch if one is pending.
>   *
>   * Return: 0 on success. -EINVAL if no delayed switch is pending, if the client
>   * has unregistered in the meantime or if there are other clients blocking the
> -- 
> 2.46.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch