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b3370311-6fa2-4717-049d-08de79505b2b X-MS-Exchange-CrossTenant-AuthSource: CYYPR11MB8430.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Mar 2026 18:11:56.9272 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: MRBD8fqv9E06biiIO8Av3hXu9m1sNaPqXU/OsSyJ8vvmmd0aI7qno4evwbbaU/FxJbqRRpQOsOgyggvE5XWBcg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR11MB8232 X-OriginatorOrg: intel.com X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On Wed, Jan 28, 2026 at 10:13:26AM +0000, Tvrtko Ursulin wrote: > The fallback case for DPT backing store is a buffer object in system > memory buffer, which by default use a write-back CPU caching policy. > > If this fallback gets triggered, and since there is currently no flushing, > the DPT writes made when pinning a buffer to display are not guaranteed to > be seen by the display engine. > > To fix this, since both the local memory and the stolen memory DPT > placement use write-combine, let us make the system memory option follow > suit by marking the buffer with the scanout flag. > > Signed-off-by: Tvrtko Ursulin > Suggested-by: Ville Syrjälä > --- > drivers/gpu/drm/xe/display/xe_fb_pin.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/xe/display/xe_fb_pin.c b/drivers/gpu/drm/xe/display/xe_fb_pin.c > index d2c4e94180fa..b285cc446f57 100644 > --- a/drivers/gpu/drm/xe/display/xe_fb_pin.c > +++ b/drivers/gpu/drm/xe/display/xe_fb_pin.c > @@ -123,7 +123,8 @@ static int __xe_pin_fb_vma_dpt(const struct intel_framebuffer *fb, > ttm_bo_type_kernel, > XE_BO_FLAG_SYSTEM | > XE_BO_FLAG_GGTT | > - XE_BO_FLAG_PAGETABLE, > + XE_BO_FLAG_PAGETABLE | > + XE_BO_FLAG_SCANOUT, /* Force WC mapping */ This kind of changes the semantics of the flag. Could you please change this internal name to something like s/XE_BO_FLAG_SCANOUT/XE_BO_FLAG_FORCE_WC Then we will have something like /* * Display scanout is always non-coherent with the CPU cache. * * For Xe_LPG and beyond up to NVL-P (excluding), PPGTT PTE * lookups are also non-coherent and require a CPU:WC mapping. */ if (args->flags & DRM_XE_GEM_CREATE_FLAG_SCANOUT) bo_flags |= XE_BO_FLAG_FORCE_WC; > alignment, false); > if (IS_ERR(dpt)) > return PTR_ERR(dpt); > -- > 2.52.0 >