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Fri, 22 May 2026 03:25:43 -0500 Received: from [10.24.50.20] (moteen-ubuntu-desk.dhcp.ti.com [10.24.50.20]) by lelvem-mr06.itg.ti.com (8.18.1/8.18.1) with ESMTP id 64M8Pe771098781; Fri, 22 May 2026 03:25:41 -0500 Message-ID: <79ab3c39-0650-43c7-81ed-8248c200ceff@ti.com> Date: Fri, 22 May 2026 13:55:39 +0530 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] serial: 8250_omap: clear rx_running on zero-length DMA completes To: Matthias Feser , "linux-serial@vger.kernel.org" , "gregkh@linuxfoundation.org" , "jirislaby@kernel.org" CC: "linux-kernel@vger.kernel.org" , "k-willis@ti.com" , "msp@baylibre.com" , "andriy.shevchenko@linux.intel.com" References: <4b8c59fe-c6a1-47cb-ab3b-855b1edddde2@ti.com> Content-Language: en-US From: Moteen Shah In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-C2ProcessedOrg: 333ef613-75bf-4e12-a4b1-8e3623f5dcea X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF000044A8:EE_|SN4PR10MB5639:EE_ X-MS-Office365-Filtering-Correlation-Id: 7e33cd1b-b810-46a0-d967-08deb7dbb7bf X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|1800799024|376014|82310400026|18002099003|22082099003|56012099003|4143699003|6133799003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:198.47.23.195;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:lewvzet201.ext.ti.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(36860700016)(1800799024)(376014)(82310400026)(18002099003)(22082099003)(56012099003)(4143699003)(6133799003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: RB6W3h0fn1Z1cmpEjqtWE5MZz3uE+W0xCG/N++0X9P+aIhN8eWzHyq4FAhbkWdEymO/48aP3GlfN9TY6eE5stNsgQj62V0N6uXBYt2aLzC03irlIkw4dTrrvODer19WdDxFgYN06R78EMrGT7M/hJOi4vtupLTqD0pKJQVC5BRXLWc/pGcXgyzmwZWIZ0k70sA0aP68r7CZalb8fbp0fvPnB1yS3yftRxjneFjFlWNj2oxrxx6bGIj/4ZQVwsCKQLcaf4nOCf5pSyWtZHhWbJX708uBqO/qnS9ng3QmO+pPzaDV6bI3+ToSk1rcgwFJiNem7W3y9y02gk3kQtftGtAzpWHqJ+9xAq6Ko+mwlTOOmwInzyLTWaC52v2vSs1KuRH6rbX7VFguIYOdS9nWFvft3sJgbArPcDRp+sendnfIBWVUjNNX7kdrj+34Nimr5 X-OriginatorOrg: ti.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 May 2026 08:25:44.0477 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7e33cd1b-b810-46a0-d967-08deb7dbb7bf X-MS-Exchange-CrossTenant-Id: e5b49634-450b-4709-8abb-1e2b19b982b7 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=e5b49634-450b-4709-8abb-1e2b19b982b7;Ip=[198.47.23.195];Helo=[lewvzet201.ext.ti.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF000044A8.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN4PR10MB5639 On 22/05/26 13:54, Matthias Feser wrote: > Thanks for the fast response. I've updated the patch accordingly. > > From: Matthias Feser > Date: Fri, 22 May 2026 10:11:16 +0200 > Subject: [PATCH v2] serial: 8250_omap: clear rx_running on zero-length DMA completes > > On AM33xx RX DMA only triggers when the FIFO reaches the > configured threshold (typically 48 bytes). For smaller bursts > no DMA request is issued and the FIFO is drained by RX timeout. > > In this case __dma_rx_do_complete() can legitimately see count == 0. > > The current code exits early in this case and does not clear > dma->rx_running, leaving the DMA state inconsistent. This can > prevent RX DMA from restarting and may cause > omap_8250_rx_dma_flush() to fail, marking DMA as broken. > > Fix this by clearing dma->rx_running once the DMA transfer has > completed or been terminated, even if no data was transferred. > > Changes in v2: > - Move dma->rx_running clear before the count check so the state > is updated immediately after DMA completion/termination > > Signed-off-by: Matthias Feser > --- > drivers/tty/serial/8250/8250_omap.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c > index c552c6b9a037..76bc8ad324cb 100644 > --- a/drivers/tty/serial/8250/8250_omap.c > +++ b/drivers/tty/serial/8250/8250_omap.c > @@ -944,11 +944,11 @@ static void __dma_rx_do_complete(struct uart_8250_port *p) > dev_err(p->port.dev, "teardown incomplete\n"); > } > } > + dma->rx_running = 0; > if (!count) > goto out; > ret = tty_insert_flip_string(tty_port, dma->rx_buf, count); > > - dma->rx_running = 0; > p->port.icount.rx += ret; > p->port.icount.buf_overrun += count - ret; > out: Reviewed-by: Moteen Shah Regards, Moteen