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charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260929-max310x-rs485-sw-delay-v5-6-ae46afa583f2@vaisala.com> References: <20260929-max310x-rs485-sw-delay-v5-0-ae46afa583f2@vaisala.com> In-Reply-To: <20260929-max310x-rs485-sw-delay-v5-0-ae46afa583f2@vaisala.com> To: Greg Kroah-Hartman , Jiri Slaby Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Hugo Villeneuve , Tapio Reijonen , Tapio Reijonen X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1790674682; l=1725; i=tapio.reijonen@vaisala.com; s=20250903; h=from:subject:message-id; bh=qyR9JiEhhdhUeQINI095zz35mQq5HJ06/6E+X6iCHPU=; b=uKFVB13SwoCpgh/wW4Px1qOtPQ5WTzfE6PXpcwr6UHesPBoobyKERgwM2LKzcZVq+HpLQXaC+ x2ubb7+RRxyC47+SAd5Jbg/iMmvzp6lN42+tIP1soRvQuC+MVRiNpuc X-Developer-Key: i=tapio.reijonen@vaisala.com; a=ed25519; pk=jWBz3VD84WbWgfEgIqB5iFFiyVIHZr52zVBPOm7qiGo= X-ClientProxiedBy: OS6P279CA0089.NORP279.PROD.OUTLOOK.COM (2603:10a6:e10:3e::11) To AM9PR06MB7907.eurprd06.prod.outlook.com (2603:10a6:20b:3a6::23) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AM9PR06MB7907:EE_|PA1PR06MB9752:EE_ X-MS-Office365-Filtering-Correlation-Id: d881e4af-a3e2-4558-7672-08df1e0d5f5b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|52116014|23010399003|376014|366016|1800799024|38350700014|56012099006|11063799006|5023799004|10067099003|22082099003|18002099003|6133799003; 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It does conflate two distinct events, though: start_tx() is the serial core starting a new transmission, while TXEMPTY can only fire for a transmission that is already running - the bit latches on the FIFO's non-empty to empty transition, and the IRQ handler's read of IRQSTS consumes the latch, so a stale TXEMPTY cannot exist on an idle port (if the bit were level-triggered, the handler's read-until-clear loop would never terminate). Schedule tx_work directly, keeping the interrupt path a pure FIFO refill. This is preparation for a following patch that adds software-timed RS485 RTS control, where start_tx() also starts the RTS envelope and a refill must not restart it. No functional change. Signed-off-by: Tapio Reijonen --- drivers/tty/serial/max310x.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c index e07fb87f21f102cfa3fdae5275cb7810be1c3dbd..8f8817b127c891f18af52bd3d24efb269db78211 100644 --- a/drivers/tty/serial/max310x.c +++ b/drivers/tty/serial/max310x.c @@ -858,8 +858,12 @@ static irqreturn_t max310x_port_irq(struct max310x_port *s, int portno) } if (rxlen) max310x_handle_rx(port, rxlen); + /* + * TXEMPTY latches on the FIFO becoming empty, so a stale + * interrupt cannot pump data during an RTS setup delay. + */ if (ists & MAX310X_IRQ_TXEMPTY_BIT) - max310x_start_tx(port); + schedule_work(&s->p[portno].tx_work); } while (1); return res; -- 2.47.3