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Wed, 28 Oct 2026 09:46:17 -0700 (PDT) Received: from localhost.localdomain ([136.126.251.209]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a23908449sm7821964eec.11.2026.10.28.09.46.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 09:46:16 -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 3/5] drm/vc4: dsi: Rate-limit error interrupt messages Date: Wed, 28 Oct 2026 09:45:28 -0700 Message-ID: <20261028164539.3471833-4-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 The error interrupts (contention, sequence and timeout errors) are always enabled and each one is logged with drm_err() from the interrupt handler. When a peripheral leaves the data lanes in a bad state, the same error is raised again as soon as it is acknowledged. On a Raspberry Pi 4 a "data lane 0 sequence error" was seen at more than 50000 interrupts per second; printing every one of them, mostly to a serial console, starved the rest of the system to the point that the SD card driver timed out and the board had to be reset. Use drm_err_ratelimited() so that the errors stay visible without taking the system down. Signed-off-by: Henry Zhang --- drivers/gpu/drm/vc4/vc4_dsi.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c index 1eea60aec..be9caaf50 100644 --- a/drivers/gpu/drm/vc4/vc4_dsi.c +++ b/drivers/gpu/drm/vc4/vc4_dsi.c @@ -1487,8 +1487,8 @@ static void dsi_handle_error(struct vc4_dsi *dsi, if (!(stat & bit)) return; - drm_err(dsi->bridge.dev, "DSI%d: %s error\n", dsi->variant->port, - type); + drm_err_ratelimited(dsi->bridge.dev, "DSI%d: %s error\n", + dsi->variant->port, type); *ret = IRQ_HANDLED; } -- 2.47.3