Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1947256AbdDYSPs (ORCPT ); Tue, 25 Apr 2017 14:15:48 -0400 Received: from laurent.telenet-ops.be ([195.130.137.89]:49110 "EHLO laurent.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1947745AbdDYSPm (ORCPT ); Tue, 25 Apr 2017 14:15:42 -0400 From: Geert Uytterhoeven To: Greg Kroah-Hartman Cc: Jiri Slaby , Richard Genoud , Yoshihiro Shimoda , linux-serial@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH] serial: sh-sci: Fix race condition causing garbage during shutdown Date: Tue, 25 Apr 2017 20:15:35 +0200 Message-Id: <1493144135-898-1-git-send-email-geert+renesas@glider.be> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2022 Lines: 66 If DMA is enabled and used, a burst of old data may be seen on the serial console during "poweroff" or "reboot". uart_flush_buffer() clears the circular buffer, but sci_port.tx_dma_len is not reset. This leads to a circular buffer overflow, dumping (UART_XMIT_SIZE - sci_port.tx_dma_len) bytes. To fix this, add a .flush_buffer() callback that resets sci_port.tx_dma_len. Inspired by commit 31ca2c63fdc0aee7 ("tty/serial: atmel: fix race condition (TX+DMA)"). Signed-off-by: Geert Uytterhoeven --- A big thanks to Richard! I had no idea what was happening here, until I saw his patch passing by in a stable backport. In v4.3 and older, the field is called sg_len_tx. --- drivers/tty/serial/sh-sci.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 9a47cc4f16a2798f..a15739202d6c75f2 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1545,7 +1545,16 @@ static void sci_free_dma(struct uart_port *port) if (s->chan_rx) sci_rx_dma_release(s, false); } -#else + +static void sci_flush_buffer(struct uart_port *port) +{ + /* + * In uart_flush_buffer(), the xmit circular buffer has just been + * cleared, so we have to reset tx_dma_len accordingly. + */ + to_sci_port(port)->tx_dma_len = 0; +} +#else /* !CONFIG_SERIAL_SH_SCI_DMA */ static inline void sci_request_dma(struct uart_port *port) { } @@ -1553,7 +1562,9 @@ static inline void sci_request_dma(struct uart_port *port) static inline void sci_free_dma(struct uart_port *port) { } -#endif + +#define sci_flush_buffer NULL +#endif /* !CONFIG_SERIAL_SH_SCI_DMA */ static irqreturn_t sci_rx_interrupt(int irq, void *ptr) { @@ -2566,6 +2577,7 @@ static const struct uart_ops sci_uart_ops = { .break_ctl = sci_break_ctl, .startup = sci_startup, .shutdown = sci_shutdown, + .flush_buffer = sci_flush_buffer, .set_termios = sci_set_termios, .pm = sci_pm, .type = sci_type, -- 2.7.4