From c004ef925faf07fda738447cfd154f247dedf73c Mon Sep 17 00:00:00 2001 From: Matthias Feser Date: Tue, 26 May 2026 07:35:09 +0000 Subject: [PATCH] serial: 8250_omap: clear rx_running on zero-length DMA completes commit 061b627ba534230a18ec4d7251562af12325d06a upstream. 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. Fixes: a5fd8945a478 ("serial: 8250: 8250_omap.c: Clear DMA RX running status only after DMA termination is done") Cc: stable Signed-off-by: Matthias Feser Reviewed-by: Moteen Shah Link: https://patch.msgid.link/BE3P281MB55155F2F5795E411F5A65282EE0B2@BE3P281MB5515.DEUP281.PROD.OUTLOOK.COM Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_omap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 776373423b2a..8796d0525f35 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -953,11 +953,12 @@ 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: