[Intel-gfx] [PATCH 1/9] drm/i915/dsb: Replace HAS_DSB check with dsb->cmd_buf check

[Ville Syrjälä]

On Fri, Jan 31, 2020 at 03:04:17PM +0530, Manna, Animesh wrote:
> 
> On 30-01-2020 23:43, Souza, Jose wrote:
> > On Wed, 2020-01-29 at 20:20 +0200, Ville Syrjala wrote:
> >> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >>
> >> We may want to not use the DSB even if the platform has one.
> >> So replace the HAS_DSB check in the _put() with a cmd_buf check
> >> that will work in either case.
> > Reviewed-by: José Roberto de Souza <jose.souza at intel.com>
> >
> >> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >> ---
> >>   drivers/gpu/drm/i915/display/intel_dsb.c | 3 +--
> >>   1 file changed, 1 insertion(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c
> >> b/drivers/gpu/drm/i915/display/intel_dsb.c
> >> index 9dd18144a664..12776f09f227 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_dsb.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> >> @@ -160,9 +160,8 @@ intel_dsb_get(struct intel_crtc *crtc)
> >>   void intel_dsb_put(struct intel_dsb *dsb)
> >>   {
> >>   	struct intel_crtc *crtc = container_of(dsb, typeof(*crtc),
> >> dsb);
> >> -	struct drm_i915_private *i915 = to_i915(crtc->base.dev);
> >>   
> >> -	if (!HAS_DSB(i915))
> >> +	if (!dsb->cmd_buf)
> 
> Ville and Jose,
> 
> Have a concern here. In intel_dsb_get() if get failure during i915_gem_object_create_internal, i915_gem_object_ggtt_pin, i915_gem_object_pin_map then we may not have dsb->cmd_buf.
> Then ref-count mechanism will break.

Hmm. Yeah. The refcount WARN could easily be fixed by either
decrementung refcount on get() fail or doing the "let's never use
DSB" patch after the refcount inc.

> I feel HAS_DSB(i915) check is better than dsb->cmd_buf otherwise need to do some cleanup is intel_dsb_get() as well.
> 
> Regards,
> Animesh
> 
> >>   		return;
> >>   
> >>   	if (WARN_ON(dsb->refcount == 0))
> > _______________________________________________
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> > Intel-gfx at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel