Re: [PATCH] serial/mxs-auart: increase time to wait for transmitter to become idle

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

Hi Greg,

On Thu, Jul 04, 2013 at 08:58:36AM -0700, Greg Kroah-Hartman wrote:
> On Thu, Jul 04, 2013 at 11:27:16AM +0200, Uwe Kleine-König wrote:
> > On Fri, Jun 28, 2013 at 11:49:41AM +0200, Uwe Kleine-König wrote:
> > > Without this patch the driver waits ~1 ms for the UART to become idle. At
> > > 115200n8 this time is (theoretically) enough to transfer 11.5 characters
> > > (= 115200 bits/s / (10 Bits/char) * 1ms). As the mxs-auart has a fifo size
> > > of 16 characters the clock is gated too early. The problem is worse for
> > > lower baud rates.
> > > 
> > > This only happens to really shut down the transmitter in the middle of a
> > > transfer if /dev/ttyAPPx isn't opened in userspace (e.g. by a getty) but
> > > was at least once (because the bootloader doesn't disable the transmitter).
> > > 
> > > So increase the timeout to 20 ms which should be enough for 9600n8, too.
> > > Moreover skip gating the clock if the timeout is elapsed.
> > > 
> > > Cc: stable@vger.kernel.org # v2.6.39+
> > > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > Any comments on this. I hoped this patch would make it in for 3.10 :-(
> 
> You sent it after my tree closed for 3.11, 3.10 is a stretch :)
You close your tree for fixes?

Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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