From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [PATCH] serial/mxs-auart: increase time to wait for transmitter to become idle Date: Thu, 4 Jul 2013 09:16:10 -0700 Message-ID: <20130704161610.GA20907@kroah.com> References: <1372413017-23252-1-git-send-email-u.kleine-koenig@pengutronix.de> <20130704092716.GC17454@pengutronix.de> <20130704155836.GA13897@kroah.com> <20130704160250.GC32260@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20130704160250.GC32260@pengutronix.de> Sender: stable-owner@vger.kernel.org To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Jiri Slaby , linux-serial@vger.kernel.org, kernel@pengutronix.de, stable@vger.kernel.org List-Id: linux-serial@vger.kernel.org On Thu, Jul 04, 2013 at 06:02:50PM +0200, Uwe Kleine-K=F6nig wrote: > Hi Greg, >=20 > 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-K=F6nig wrote: > > > On Fri, Jun 28, 2013 at 11:49:41AM +0200, Uwe Kleine-K=F6nig wrot= e: > > > > Without this patch the driver waits ~1 ms for the UART to becom= e idle. At > > > > 115200n8 this time is (theoretically) enough to transfer 11.5 c= haracters > > > > (=3D 115200 bits/s / (10 Bits/char) * 1ms). As the mxs-auart ha= s a fifo size > > > > of 16 characters the clock is gated too early. The problem is w= orse for > > > > lower baud rates. > > > >=20 > > > > This only happens to really shut down the transmitter in the mi= ddle of a > > > > transfer if /dev/ttyAPPx isn't opened in userspace (e.g. by a g= etty) but > > > > was at least once (because the bootloader doesn't disable the t= ransmitter). > > > >=20 > > > > So increase the timeout to 20 ms which should be enough for 960= 0n8, too. > > > > Moreover skip gating the clock if the timeout is elapsed. > > > >=20 > > > > Cc: stable@vger.kernel.org # v2.6.39+ > > > > Signed-off-by: Uwe Kleine-K=F6nig > > > Any comments on this. I hoped this patch would make it in for 3.1= 0 :-( > >=20 > > You sent it after my tree closed for 3.11, 3.10 is a stretch :) > You close your tree for fixes? 2 days before the kernel is to be released? Yes, I do. This will get into 3.11-rc2 or -rc3, and backported to 3.10 and others, so please jus= t give it a bit of time. It's just a driver issue, nothing keeping machines from booting properly :) thanks, greg k-h