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Wed, 28 Oct 2026 09:46:16 -0700 (PDT) Received: from localhost.localdomain ([136.126.251.209]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a23908449sm7821964eec.11.2026.10.28.09.46.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 09:46:15 -0700 (PDT) From: Henry Zhang To: Maxime Ripard , Dave Stevenson Cc: Henry Zhang , =?UTF-8?q?Ma=C3=ADra=20Canal?= , Raspberry Pi Kernel Maintenance , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 2/5] drm/vc4: dsi: Don't return error reports as read data Date: Wed, 28 Oct 2026 09:45:27 -0700 Message-ID: <20261028164539.3471833-3-henryzhang62@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261028164539.3471833-1-henryzhang62@gmail.com> References: <20261028164539.3471833-1-henryzhang62@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 When a DSI peripheral detects an error, for example contention during the bus turnaround, it may answer a read request with an Acknowledge and Error Report short packet instead of the read response. vc4_dsi_host_transfer() does not check the type of the received packet (there is a FINISHME for it). It copies the two bytes of the error report into the caller's buffer and returns success, so the caller gets the error bits as if they were register contents. Packets received with a checksum error, an uncorrectable ECC error or incomplete are passed on the same way. Return -EIO in these cases so that callers can tell a failed read from data, and retry if they want to. Reviewed-by: Dave Stevenson Signed-off-by: Henry Zhang --- drivers/gpu/drm/vc4/vc4_dsi.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c index aa2b46fb0..1eea60aec 100644 --- a/drivers/gpu/drm/vc4/vc4_dsi.c +++ b/drivers/gpu/drm/vc4/vc4_dsi.c @@ -39,6 +39,8 @@ #include #include +#include