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

From: Sinclair Yeh <syeh@vmware.com>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	VMware Graphics <linux-graphics-maintainer@vmware.com>,
	Deepak Rawat <drawat@vmware.com>
Subject: Re: [PATCH v2 02/13] drm/vmwgfx: Stop using plane->fb in vmw_kms_helper_dirty()
Date: Mon, 4 Jun 2018 11:13:53 -0700	[thread overview]
Message-ID: <20180604181352.GA31191@vmware.com> (raw)
In-Reply-To: <20180530200857.GS23723@intel.com>

On Wed, May 30, 2018 at 11:08:57PM +0300, Ville Syrjälä wrote:
> 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)?

Eitherway is fine with me.

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