From linux-omap-owner@vger.kernel.org Tue Jul 15 21:23:13 2008 Received: from localhost ([127.0.0.1] helo=dominion ident=koen) by dominion.dominion.void with esmtp (Exim 4.69) (envelope-from ) id 1KIq7E-0004FX-VS for koen@localhost; Tue, 15 Jul 2008 21:23:13 +0200 Received: from xs.service.utwente.nl [130.89.5.250] by dominion with POP3 (fetchmail-6.3.6) for (single-drop); Tue, 15 Jul 2008 21:23:12 +0200 (CEST) Received: from mail.service.utwente.nl ([130.89.5.254]) by exchange.service.utwente.nl with Microsoft SMTPSVC(6.0.3790.3959); Tue, 15 Jul 2008 21:01:02 +0200 Received: from mx.utwente.nl ([130.89.2.12]) by mail.service.utwente.nl with Microsoft SMTPSVC(6.0.3790.3959); Tue, 15 Jul 2008 21:01:01 +0200 Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by mx.utwente.nl (8.12.10/SuSE Linux 0.7) with ESMTP id m6FJ0qDf031889 for ; Tue, 15 Jul 2008 21:00:52 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756776AbYGOTAV (ORCPT ); Tue, 15 Jul 2008 15:00:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755065AbYGOTAV (ORCPT ); Tue, 15 Jul 2008 15:00:21 -0400 Received: from utopia.booyaka.com ([72.9.107.138]:35569 "EHLO utopia.booyaka.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756776AbYGOTAU (ORCPT ); Tue, 15 Jul 2008 15:00:20 -0400 Received: (qmail 2982 invoked by uid 526); 15 Jul 2008 19:00:18 -0000 Date: Tue, 15 Jul 2008 13:00:18 -0600 (MDT) From: Paul Walmsley To: linux-omap@vger.kernel.org Subject: [PATCH] i2c-omap: close suspected race between omap_i2c_idle() and omap_i2c_isr() Message-ID: User-Agent: Alpine 1.00 (DEB 882 2007-12-20) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-UTwente-MailScanner-Information: Scanned by MailScanner. Contact servicedesk@icts.utwente.nl for more information. X-UTwente-MailScanner: Found to be clean X-UTwente-MailScanner-From: linux-omap-owner@vger.kernel.org X-Spam-Status: No X-OriginalArrivalTime: 15 Jul 2008 19:01:01.0610 (UTC) FILETIME=[1FBA68A0:01C8E6AD] omap_i2c_idle() sets an internal flag, "dev->idle", instructing its ISR to decline interrupts. It sets this flag before it actually masks the interrupts on the I2C controller. This is problematic, since an I2C interrupt could arrive after dev->idle is set, but before the interrupt source is masked. When this happens, Linux disables the I2C controller's IRQ, causing all future transactions on the bus to fail. Symptoms, happening on about 7% of boots: irq 56: nobody cared (try booting with the "irqpoll" option) Disabling IRQ #56 i2c_omap i2c_omap.1: controller timed out In omap_i2c_idle(), this patch sets dev->idle only after the interrupt mask write to the I2C controller has left the ARM write buffer. That's probably the major offender. For additional prophylaxis, in omap_i2c_unidle(), the patch clears the dev->idle flag before interrupts are enabled, rather than afterwards. The patch has survived twenty-two reboots on the 3430SDP here without wedging I2C1. Not absolutely dispositive, but promising! Signed-off-by: Paul Walmsley --- drivers/i2c/busses/i2c-omap.c | 10 ++++++++-- 1 files changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index 55779f5..ed7e9ad 100644 --- a/drivers/i2c/busses/i2c-omap.c +++ b/drivers/i2c/busses/i2c-omap.c @@ -209,22 +209,28 @@ static void omap_i2c_unidle(struct omap_i2c_dev *dev) if (dev->iclk != NULL) clk_enable(dev->iclk); clk_enable(dev->fclk); + dev->idle = 0; if (dev->iestate) omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate); - dev->idle = 0; } static void omap_i2c_idle(struct omap_i2c_dev *dev) { u16 iv; - dev->idle = 1; dev->iestate = omap_i2c_read_reg(dev, OMAP_I2C_IE_REG); omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, 0); if (dev->rev1) iv = omap_i2c_read_reg(dev, OMAP_I2C_IV_REG); else omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, dev->iestate); + /* + * The wmb() is to ensure that the I2C interrupt mask write + * reaches the I2C controller before the dev->idle store + * occurs. + */ + wmb(); + dev->idle = 1; clk_disable(dev->fclk); if (dev->iclk != NULL) clk_disable(dev->iclk); -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html