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Fri, 22 May 2026 00:40:16 -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 64M5eDph843356; Fri, 22 May 2026 00:40:14 -0500 Message-ID: <4b8c59fe-c6a1-47cb-ab3b-855b1edddde2@ti.com> Date: Fri, 22 May 2026 11:10:12 +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] 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: 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: SJ1PEPF00002311:EE_|LV3PR10MB7913:EE_ X-MS-Office365-Filtering-Correlation-Id: 6c4a0142-b179-40ac-9677-08deb7c49e19 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700016|376014|82310400026|6133799003|22082099003|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:198.47.21.195;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:flwvzet201.ext.ti.com;PTR:ErrorRetry;CAT:NONE;SFS:(13230040)(1800799024)(36860700016)(376014)(82310400026)(6133799003)(22082099003)(56012099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: GsJdeKGHECsbd5sLZvbT+ohp2e7fUEAMkvUSe/MJddAcVcm54RMPjPYxadBAUq9EYE1oQQFlEAQBamBRnSeWAjfdYVzMS8GbXMSclRFGOd7JiOKgRIa6uyTEnjAZDYU1Xy47rZ+eeLkRZcTylUx4Y/HzwNONe6lKjwrFSaq9tcJaeQUbUNdILEWUmBGbbWRZdDbMV1uB2TSbitYxe2btaCiDb11S1jYVyaSvB3UWBAQJGZbKW0LYdqbpbf/MCH/0xV+xxFcqCDKR1w2PX5pbmzO2iPwVmZOBsj+mZyvqDw+aLbufc3/QzN9Ey+S4JOR+3v2TjkZepumwT00G0muKIvoaQT6CU3hNf3JVqKdm/J0QSnMA4HLWkJIoOP0V2x3VobJZm1jSBze8Du4u50AYYTQizklg5UqKzxZ942EOUQl3Do+MUMN7mt0UnNL2UDZT X-OriginatorOrg: ti.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 May 2026 05:40:22.5842 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6c4a0142-b179-40ac-9677-08deb7c49e19 X-MS-Exchange-CrossTenant-Id: e5b49634-450b-4709-8abb-1e2b19b982b7 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=e5b49634-450b-4709-8abb-1e2b19b982b7;Ip=[198.47.21.195];Helo=[flwvzet201.ext.ti.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF00002311.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR10MB7913 Hey Matthias, Thanks for the patch. On 21/05/26 19:00, Matthias Feser wrote: > 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 always clearing dma->rx_running on exit. > > 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..686e54859aa5 100644 > --- a/drivers/tty/serial/8250/8250_omap.c > +++ b/drivers/tty/serial/8250/8250_omap.c > @@ -948,11 +948,11 @@ static void __dma_rx_do_complete(struct uart_8250_port *p) > 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: > > + dma->rx_running = 0; > tty_flip_buffer_push(tty_port); > } > I think the better place should be just before the If(!count) check, this would mark the running status of the DMA as soon as the termination gets done. Regards, Moteen