[PATCH 1/3] drm/vmwgfx: Drop svga_lock

[Daniel Vetter]

Hi Roland,

Hopefully you had a nice start into the new year! Ping for some
review/testing on this series.

Thanks, Daniel

On Fri, Dec 11, 2020 at 5:29 PM Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>
> This isn't actually protecting anything becuase:
> - when running, ttm_resource_manager->use_type is protected through
>   vmw_private->reservation_semaphore against concurrent execbuf or
>   well anything else that might evict or reserve buffers
> - during suspend/resume there's nothing else running, hence
>   vmw_pm_freeze and vmw_pm_restore do not need to take the same lock.
> - this also holds for the SVGA_REG_ENABLE register write
>
> Hence it is safe to just remove that spinlock.
>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Cc: VMware Graphics <linux-graphics-maintainer at vmware.com>
> Cc: Roland Scheidegger <sroland at vmware.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 10 +---------
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.h |  1 -
>  2 files changed, 1 insertion(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> index 0008be02d31c..204f7a1830f0 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
> @@ -672,7 +672,6 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
>         spin_lock_init(&dev_priv->hw_lock);
>         spin_lock_init(&dev_priv->waiter_lock);
>         spin_lock_init(&dev_priv->cap_lock);
> -       spin_lock_init(&dev_priv->svga_lock);
>         spin_lock_init(&dev_priv->cursor_lock);
>
>         for (i = vmw_res_context; i < vmw_res_max; ++i) {
> @@ -1189,12 +1188,10 @@ static void __vmw_svga_enable(struct vmw_private *dev_priv)
>  {
>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>
> -       spin_lock(&dev_priv->svga_lock);
>         if (!ttm_resource_manager_used(man)) {
>                 vmw_write(dev_priv, SVGA_REG_ENABLE, SVGA_REG_ENABLE);
>                 ttm_resource_manager_set_used(man, true);
>         }
> -       spin_unlock(&dev_priv->svga_lock);
>  }
>
>  /**
> @@ -1220,14 +1217,12 @@ static void __vmw_svga_disable(struct vmw_private *dev_priv)
>  {
>         struct ttm_resource_manager *man = ttm_manager_type(&dev_priv->bdev, TTM_PL_VRAM);
>
> -       spin_lock(&dev_priv->svga_lock);
>         if (ttm_resource_manager_used(man)) {
>                 ttm_resource_manager_set_used(man, false);
>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
>                           SVGA_REG_ENABLE_HIDE |
>                           SVGA_REG_ENABLE_ENABLE);
>         }
> -       spin_unlock(&dev_priv->svga_lock);
>  }
>
>  /**
> @@ -1254,17 +1249,14 @@ void vmw_svga_disable(struct vmw_private *dev_priv)
>          */
>         vmw_kms_lost_device(dev_priv->dev);
>         ttm_write_lock(&dev_priv->reservation_sem, false);
> -       spin_lock(&dev_priv->svga_lock);
>         if (ttm_resource_manager_used(man)) {
>                 ttm_resource_manager_set_used(man, false);
> -               spin_unlock(&dev_priv->svga_lock);
>                 if (ttm_resource_manager_evict_all(&dev_priv->bdev, man))
>                         DRM_ERROR("Failed evicting VRAM buffers.\n");
>                 vmw_write(dev_priv, SVGA_REG_ENABLE,
>                           SVGA_REG_ENABLE_HIDE |
>                           SVGA_REG_ENABLE_ENABLE);
> -       } else
> -               spin_unlock(&dev_priv->svga_lock);
> +       }
>         ttm_write_unlock(&dev_priv->reservation_sem);
>  }
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> index 5b9a28157dd3..715f2bfee08a 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> @@ -596,7 +596,6 @@ struct vmw_private {
>
>         bool stealth;
>         bool enable_fb;
> -       spinlock_t svga_lock;
>
>         /**
>          * PM management.
> --
> 2.29.2
>


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