3.16.75-rc1 review patch. If anyone has any objections, please let me know.
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From: "George G. Davis" george_davis@mentor.com
commit 099506cbbc79c0bd52b19cb6b930f256dabc3950 upstream.
As noted in commit 84b40e3b57ee ("serial: 8250: omap: Disable DMA for console UART"), UART console lines use low-level PIO only access functions which will conflict with use of the line when DMA is enabled, e.g. when the console line is also used for systemd messages. So disable DMA support for UART console lines.
Reported-by: Michael Rodin mrodin@de.adit-jv.com Link: https://patchwork.kernel.org/patch/10929511/ Tested-by: Eugeniu Rosca erosca@de.adit-jv.com Reviewed-by: Simon Horman horms+renesas@verge.net.au Reviewed-by: Wolfram Sang wsa+renesas@sang-engineering.com Reviewed-by: Geert Uytterhoeven geert+renesas@glider.be Signed-off-by: George G. Davis george_davis@mentor.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/tty/serial/sh-sci.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1600,6 +1600,13 @@ static void sci_request_dma(struct uart_
dev_dbg(port->dev, "%s: port %d\n", __func__, port->line);
+ /* + * DMA on console may interfere with Kernel log messages which use + * plain putchar(). So, simply don't use it with a console. + */ + if (uart_console(port)) + return; + if (s->cfg->dma_slave_tx <= 0 || s->cfg->dma_slave_rx <= 0) return;