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Commit 1cf4a7ef authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Greg Kroah-Hartman
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serial: sh-sci: Fix race condition causing garbage during shutdown 



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 31ca2c63 ("tty/serial: atmel: fix race
condition (TX+DMA)").

Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7fbcf3af

drivers/tty/serial/sh-sci.c

+14 −2
Original line number Diff line number Diff line
@@ -1558,7 +1558,16 @@ 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)

{

}
@@ -1566,7 +1575,9 @@ 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)

{
@@ -2581,6 +2592,7 @@ 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,