From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753406Ab2DWF5F (ORCPT ); Mon, 23 Apr 2012 01:57:05 -0400 Received: from portal.weinmann.de ([62.8.140.122]:36362 "EHLO portal.weinmann.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751218Ab2DWF5C (ORCPT ); Mon, 23 Apr 2012 01:57:02 -0400 X-Greylist: delayed 976 seconds by postgrey-1.27 at vger.kernel.org; Mon, 23 Apr 2012 01:57:02 EDT From: "Voss, Nikolaus" To: "'devel@ayanes.com'" , "'Wolfram Sang'" , "'linux-arm-kernel@lists.infradead.org'" , "'linux-kernel@vger.kernel.org'" , "'linux-i2c@vger.kernel.org'" CC: "'Hubert Feurstein'" , "'rmallon@gmail.com'" , "'nicolas.ferre@atmel.com'" , "'balbi@ti.com'" , "'ben-linux@fluff.org'" Date: Mon, 23 Apr 2012 07:39:55 +0200 Subject: RE: [PATCH] i2c-at91: fix data-loss issue Thread-Topic: [PATCH] i2c-at91: fix data-loss issue Thread-Index: Ac0f9Z4QqT/60+SuSluJeNo9YSiwigBGF3mw Message-ID: References: <20120413103937.GH7154@arwen.pp.htv.fi> <1334317476-10044-1-git-send-email-h.feurstein@gmail.com> <20120418143920.GA19802@pengutronix.de> <4F930B77.8070909@ayanes.com> In-Reply-To: <4F930B77.8070909@ayanes.com> Accept-Language: en-US, de-DE Content-Language: de-DE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US, de-DE Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id q3N5w2Tf018607 Adrian Yanes wrote on 2012-04-21: > On the other hand we found that the Underrun Error (UNRE) is not handled > in the driver. When we send data up > 2-4 bytes (quite random to say > when it really fails) and we add some dev_dbg() to print > dev->transfer_status we get 141 (==UNRE). According with the datasheet, > after the first UNRE received "this action automatically generated a > STOP bit in Master Mode. Reset by read in TWI_SR when TXCOMP is set." > > We thought that one possibility for this was that the board was too slow > to process the requests or that other interrupts were interfering. > Disabling the interrupts inside of the twi interrupt handler did not > help either. > > The datasheet does not mention any method to implement some mechanism to > avoid the UNRE telling the hardware to wait a bit longer for the next > byte. Thus, one way will be to restart the transfer with the remaining > bytes (maybe only applicable to at91rm9200) or just to return some > error/message to userland informing that could not send all the data. The latter is probably the easiest and most transparent solution. There is no UNRE on G45, it just pauses the clock on an underrun condition. So in case UNRE is set, EIO should be returned similar to the already handled OVRE: diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c index a6f9e73..a84e19b 100644 --- a/drivers/i2c/busses/i2c-at91.c +++ b/drivers/i2c/busses/i2c-at91.c @@ -238,6 +238,11 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) dev_err(dev->dev, "overrun while reading\n"); return -EIO; } + if (dev->transfer_status & AT91_TWI_UNRE && dev->is_rm9200) { + dev_err(dev->dev, "underrun while writing\n"); + return -EIO; + } + dev_dbg(dev->dev, "transfer complete\n"); return 0; {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I