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[2403:5803:1750:0:d1fd:685c:f50c:5901]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b197d32ea0sm15422530a91.15.2026.11.14.19.08.53 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 14 Nov 2026 19:08:57 -0800 (PST) From: Ed Schofield To: Atharva Tiwari Cc: Doitall , Andre Eikmeyer , Alex Deucher , =?UTF-8?q?Christian=20K=C3=B6nig?= , David Airlie , Simona Vetter , Harry Wentland , Leo Li , Rodrigo Siqueira , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] drm/amd/amdgpu: Add 5K Support for iMac20,1 and iMac20,2 Date: Sun, 15 Nov 2026 14:08:48 +1100 Message-ID: <20261115030848.17705-1-ed@charmerstraining.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20261113214721.9382-1-atharvatiwarilinuxdev@gmail.com> References: <20261113214721.9382-1-atharvatiwarilinuxdev@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Atharva, Thanks for posting this. I've built v2 unchanged and tested it on my iMac20,1 over the weekend (on 7.3 plus the t2linux patches). It works well in normal use. I ran automated tests over 32 boots, 55 display off/on cycles and about 40 suspend/resume cycles, and both halves of the panel came back at 2560x2880 and 10 bpc every time, including from scaled modes. However, your v2 hangs the GPU when the two halves are set to different modes. This happened 3 times out of 3, just as with my very similar "r2" variant that I described in [1]. To reproduce this, leave the left half (eDP) at 2560x2880, set the right half (DP-1) to 2048x2304, which its EDID advertises, then start a second program that uses the GPU. Each time the log showed: amdgpu: SMU: No response msg_reg: 2a resp_reg: 0 amdgpu: Failed to disable gfxoff! (repeated four times, about 4 s apart) amdgpu: ring sdma1 timeout, signaled seq=17, emitted seq=19 amdgpu: Ring sdma1 reset failed amdgpu: GPU reset begin! The reset never finishes and the machine has to be rebooted. Since the halves are separate connectors, anything that sets modes per connector can trigger this. I think the cause is the early "return true" in resource_are_streams_timing_synchronizable(), which tells DC the two streams are synchronized even when their timings differ. Taking the shortcut only when the timings really match avoids the hang: if (stream1->ctx->dc->config.imac5K_support && stream1->timing.h_total == stream2->timing.h_total && stream1->timing.v_total == stream2->timing.v_total && stream1->timing.pix_clk_100hz == stream2->timing.pix_clk_100hz && ((stream1->signal == SIGNAL_TYPE_EDP && ... With that check, the same test passed 9 times out of 9 on a kernel ("r3" [2]) that is otherwise very close to your v2, and the normal 5K case still takes the shortcut. Without the check it failed 7 times out of 7 before v2, so the result is consistent. Dropping the shortcut altogether also passed (8 of 8, "r1" [3]). Could you add that check in v3? I'm happy to retest quickly. One note: my Tested-by and Signed-off-by tags were added before I had seen or tested this version. I'm glad to give both for a version with the check above. Please use ed@charmerstraining.com. Thanks again for all your work on this! Ed [1] https://github.com/t2linux/wiki/issues/743#issuecomment-6588960822 [2] https://github.com/edschofield/linux-t2-patches/blob/7273823e425200e9f371e9272e02ebf9abb6f1c2/7003-amdgpu-add-support-for-5K.patch [3] https://github.com/edschofield/linux-t2-patches/blob/5d3775923bf481c487ff96efc8fb3e24ecf8c9cd/7003-amdgpu-add-support-for-5K.patch