Re: [PATCH v2 02/13] drm/vmwgfx: Stop using plane->fb in vmw_kms_helper_dirty()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, May 25, 2018 at 09:50:34PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Instead of plane->fb (which we're going to deprecate for atomic drivers)
> we need to look at plane->state->fb. The maze of code leading to
> vmw_kms_helper_dirty() wasn't particularly clear, but my analysis
> concluded that the calls originating from vmw_*_primary_plane_atomic_update()
> all pass in the crtc which means we'll never end up in this branch
> of the function. All other callers use drm_modeset_lock_all() somewhere
> higher up, which means accessing plane->state is safe. We'll toss in
> a lockdep assert to catch wrongdoers.
> 
> v2: Drop the comment and make the code do what it did before (Thomas)
> 
> Cc: Deepak Rawat <drawat@vmware.com>
> Cc: Thomas Hellstrom <thellstrom@vmware.com>
> Cc: Sinclair Yeh <syeh@vmware.com>
> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> index 2e4c38bb846d..5417eb1b486e 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> @@ -2326,9 +2326,12 @@ int vmw_kms_helper_dirty(struct vmw_private *dev_priv,
>  	} else {
>  		list_for_each_entry(crtc, &dev_priv->dev->mode_config.crtc_list,
>  				    head) {
> -			if (crtc->primary->fb != &framebuffer->base)
> -				continue;
> -			units[num_units++] = vmw_crtc_to_du(crtc);
> +			struct drm_plane *plane = crtc->primary;
> +
> +			lockdep_assert_held(&plane->mutex);

kbuild test robot told me
>> include/linux/lockdep.h:347:52: error: 'struct drm_modeset_lock' has
>> no member named 'dep_map'                      
    #define lockdep_is_held(lock)  lock_is_held(&(lock)->dep_map)                                                      

Maybe I'll just drop the asserts? Or do people really want them
(in which case I gues I need to dig out the underlying mutex)?

> +
> +			if (plane->state->fb == &framebuffer->base)
> +				units[num_units++] = vmw_crtc_to_du(crtc);
>  		}
>  	}
>  
> -- 
> 2.16.1

-- 
Ville Syrjälä
Intel
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