From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hector Palacios Subject: Re: mxs auart timeout waiting for transmission with hw flow control Date: Mon, 30 Sep 2013 18:41:25 +0200 Message-ID: <5249A9B5.2080903@digi.com> References: <5249A1B7.4000404@digi.com> <20130930162044.GG2548@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail1.bemta7.messagelabs.com ([216.82.254.105]:8681 "EHLO mail1.bemta7.messagelabs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755362Ab3I3Qs3 (ORCPT ); Mon, 30 Sep 2013 12:48:29 -0400 In-Reply-To: <20130930162044.GG2548@pengutronix.de> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: =?ISO-8859-1?Q?Uwe_Kleine-K=F6nig?= Cc: "linux-serial@vger.kernel.org" , Huang Shijie , "shawn.guo@linaro.org" , "fabio.estevam@freescale.com" , Marek Vasut Hi Uwe, On 09/30/2013 06:20 PM, Uwe Kleine-K=F6nig wrote: > Hi Hector, > > On Mon, Sep 30, 2013 at 06:07:19PM +0200, Hector Palacios wrote: >> I saw your patch at >> http://www.spinics.net/lists/stable/msg12952.html and I believe I'm >> having a similar issue when not using the port as console. >> >> With hardware flow control enabled transmission fails at low >> baudrates (9600,38400). Apparently the transmitter closes the port > Which kernel are you using? I think there were some other fixes > concering flow control some time ago. v3.10. The driver is pretty close to current status. >> before the data has been really shifted out (or even transferred by >> the DMA). While the console functions check the status of >> AUART_STAT_BUSY, the standard functions don't, and the AUART is busy >> when shutdown is called at low baudrates. >> >> I also see the function uart_wait_until_sent() of serial_core.c >> getting out with timeout expired. At 9600 baud, this function waits >> 2 or 4 jiffies. Increasing (a lot) the timeout of this function >> solves the problem. I monitored the time it takes for TX to be empty >> and it resulted in sometimes around 200 jiffies (@9600). > Again with flow control and another imx28 on the opposite side? Does = it > work without flow control? Is CTS busy for some time? In that case a > simple timeout isn't appropriate. Using console and flow control on t= he > same port might be hairy, not sure though. Yes, two imx28 devices with hw flow control enabled. Without flow contr= ol it works. CTS is not busy. At these low baudrates the CPU is fast enough to proce= ss the received=20 data in time. I'm not using the AUART as console but as a standard port. >> The issue can be reproduced using two iMX28 devices (transmitting >> between two ports on the same platform usually works fine), >> configuring a low baudrate (9600) and hardware flow enabled, and >> sending a file of 40K, for example. The last ~200 bytes or so are >> typically not sent over the line. > I currently don't have the time and machines to test, but maybe the > freescale guys (added Fabio to Cc, too) might want to test it. > > Best regards from Freiburg I wish I could drop by Freiburg one of these days! Love the city (and t= he beer). Best regards, -- Hector Palacios -- To unsubscribe from this list: send the line "unsubscribe linux-serial"= in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html