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

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Jan 14, 2021 at 04:31:09PM +0100, Roland Scheidegger wrote:
> Hi,
> 
> looking at it, seems alright. Not sure why the lock was supposedly
> needed, maybe it was at some point (it seems like all usage of this lock
> was introduced way back in 2015, commit 153b3d5b037ee).
> 
> For the series: Reviewed-by: Roland Scheidegger <sroland@vmware.com>

Series merged, thanks for taking a look.
-Daniel

> 
> Roland
> 
> Am 12.01.21 um 09:49 schrieb 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@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@intel.com>
> >> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> >> Cc: Roland Scheidegger <sroland@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
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