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[68.235.46.62]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-532eb399581sm21911581cf.28.2026.09.23.09.01.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 09:01:31 -0700 (PDT) From: Fabio Piparo To: Thomas Zimmermann Cc: Javier Martinez Canillas , dri-devel@lists.freedesktop.org, Fabio Piparo Subject: Re: drm/ssd130x: stale pixels when the GPU renders into the framebuffer Date: Wed, 23 Sep 2026 12:00:49 -0400 Message-ID: <20260923160049.1741651-1-holofermes@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <1f383114-e367-4b67-899b-14a393fece94@suse.de> References: <1f383114-e367-4b67-899b-14a393fece94@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Fri, 25 Sep 2026 07:30:44 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Thomas, Thanks for taking a look. On 14.09.26 10:43, Thomas Zimmermann wrote: > I assume you write these frames quickly one after the other? As i2c is > really slow, you might write to buffers that are still being transferred > in the background. > > Do you read back the status of the page flips? DRM should tell you when > it has completed transferring a frame. See [1] The test renders with the GPU: two dumb buffers allocated on the ssd130x device and shared with v3d over PRIME. It runs at 10 fps. Before each flip it calls glFinish(), then flips with DRM_MODE_PAGE_FLIP_EVENT and waits for the event before drawing into the other buffer. The same test drawing with the CPU instead comes out clean. I'm happy to send the test program if it would help. Best regards, Fabio