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serial: sh-sci: Improve comments for DMA timeout calculation 

Reformat, grammar improvements, use "ms" instead of "msec".

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Geert Uytterhoeven 2015-08-21 20:02:38 +02:00 committed by Greg Kroah-Hartman
parent beb9487b0c
commit f5835c1d0e
1 changed files with 7 additions and 7 deletions
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14
drivers/tty/serial/sh-sci.c
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@ -2015,13 +2015,13 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
#ifdef CONFIG_SERIAL_SH_SCI_DMA
/*
* Calculate delay for 2 DMA buffers (4 FIFO).
* See serial_core.c::uart_update_timeout(). With 10
* bits (CS8), 250Hz, 115200 baud and 64 bytes FIFO, the above function
* calculates 1 jiffie for the data plus 5 jiffies for the "slop(e)."
* Then below we calculate 5 jiffies (20ms) for 2 DMA buffers (4 FIFO
* sizes), but when performing a faster transfer, value obtained by
* this formula is may not enough. Therefore, if value is smaller than
* 20msec, this sets 20msec as timeout of DMA.
* See serial_core.c::uart_update_timeout().
* With 10 bits (CS8), 250Hz, 115200 baud and 64 bytes FIFO, the above
* function calculates 1 jiffie for the data plus 5 jiffies for the
* "slop(e)." Then below we calculate 5 jiffies (20ms) for 2 DMA
* buffers (4 FIFO sizes), but when performing a faster transfer, the
* value obtained by this formula is too small. Therefore, if the value
* is smaller than 20ms, use 20ms as the timeout value for DMA.
*/
if (s->chan_rx) {
unsigned int bits;