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([240e:36d:b09:1810:7fff:6550:13f4:b6f6]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-892bba97a22sm80118b3a.49.2026.10.07.06.15.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Oct 2026 06:16:15 -0700 (PDT) From: Jianfeng Liu To: robin.clark@oss.qualcomm.com Cc: abelvesa@kernel.org, abhinav.kumar@linux.dev, acelan.kao@canonical.com, airlied@gmail.com, akuchynski@chromium.org, bleung@chromium.org, christian.koenig@amd.com, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, gregkh@linuxfoundation.org, heikki.krogerus@linux.intel.com, jesszhan0024@gmail.com, johan@kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, liujianfeng1994@gmail.com, lumag@kernel.org, marijn.suijten@somainline.org, pooja.katiyar@intel.com, sean@poorly.run, simona@ffwll.ch, yuanhsinte@chromium.org Subject: Re: [RFT 0/5] drm/msm: DMABUF_DEBUG fixes Date: Wed, 7 Oct 2026 21:15:43 +0800 Message-ID: <20261007131543.7634-1-liujianfeng1994@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261006131000.81501-1-robin.clark@oss.qualcomm.com> References: <20261006131000.81501-1-robin.clark@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Rob, On Tue, Oct 6, 2026 at 6:09 AM Rob Clark wrote: > With DMABUF_DEBUG=y, the page information is stripped from the sgt that > we get for an externally allocated buffer that is dma-buf imported (as > opposed to an exported GEM buffer that is re-imported). [...] Tested on the machine that originally reported the breakage - this exercises exactly the externally-allocated-buffer case from your cover letter: Tested-by: Jianfeng Liu # x1e78100 (Acer SFA14-11), v7.3-rc5 + this series, CONFIG_DMABUF_DEBUG=y Hardware video decode in chromium (V4L2 decoder capture buffers from videobuf2-dma-contig imported into msm and rendered by the GPU) displays correctly, with zero arm-smmu faults and zero io-pgtable WARNs. For comparison, on plain v7.3-rc5 with DMABUF_DEBUG=y the same workload logs UCHE translation faults and a __arm_lpae_unmap() WARN storm (~470 traces per minute of playback). This is also much cleaner than the translation-based approach in the follow-up series I withdrew - mapping from the DMA addresses is where I should have ended up in the first place. One small suggestion for __do_map(): panthor treats "map_pages() mapped nothing" as an error (panthor_mmu.c): /* If nothing was mapped, consider it an ENOMEM. */ if (!ret && !mapped) ret = -ENOMEM; With the DMA fields now populated on both paths this should not trigger in practice, but it would turn any future regression back into a loud failure instead of a silent empty mapping - which is the failure mode this whole series fixes. Happy to run more (heap-exported dmabuf import test, kmssink scanout of V4L2 frames) on any revision. BR, Jianfeng