linux-kernel - [PATCH 3.12 023/146] 8250_core: Fix unwanted TX chars write

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Message-Id: <9ebff4b62caaf11ad6a701f8c4905411410b7728.1402303820.git.jslaby@suse.cz>
Date:	Mon,  9 Jun 2014 10:49:18 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Loic Poulain <loic.poulain@...el.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 023/146] 8250_core: Fix unwanted TX chars write

From: Loic Poulain <loic.poulain@...el.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit b08c9c317e3f7764a91d522cd031639ba42b98cc upstream.

On transmit-hold-register empty, serial8250_tx_chars
should be called only if we don't use DMA.
DMA has its own tx cycle.

Signed-off-by: Loic Poulain <loic.poulain@...el.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/tty/serial/8250/8250_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index aa6db8f4ee18..bf9d2ac9c9ed 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1520,7 +1520,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 			status = serial8250_rx_chars(up, status);
 	}
 	serial8250_modem_status(up);
-	if (status & UART_LSR_THRE)
+	if (!up->dma && (status & UART_LSR_THRE))
 		serial8250_tx_chars(up);
 
 	spin_unlock_irqrestore(&port->lock, flags);
-- 
1.9.3

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