From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaro Koskinen Subject: Re: [PATCH v2 2/2] omap i2c: add a timeout to the busy waiting Date: Thu, 25 Mar 2010 16:38:09 +0200 Message-ID: <4BAB7551.6040203@nokia.com> References: <20100316143025.GR2900@atomide.com> <1269510757-8119-3-git-send-email-virtuoso@slind.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1269510757-8119-3-git-send-email-virtuoso-0lOfPCoBze7YtjvyW6yDsg@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: ext Alexander Shishkin Cc: "ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org" , "nm-l0cyMroinI0@public.gmane.org" , "linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Tony Lindgren List-Id: linux-i2c@vger.kernel.org Hi, Alexander Shishkin wrote: > The errata 1.153 workaround is busy waiting on XUDF bit in interrupt > context, which may lead to kernel hangs. The problem can be reproduced > by running the bus with wrong (too high) speed. > > Signed-off-by: Alexander Shishkin > Acked-by: Tony Lindgren > CC: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > CC: linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > CC: nm-l0cyMroinI0@public.gmane.org > --- > drivers/i2c/busses/i2c-omap.c | 8 ++++++++ > 1 files changed, 8 insertions(+), 0 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > index 2d146ac..7d56a25 100644 > --- a/drivers/i2c/busses/i2c-omap.c > +++ b/drivers/i2c/busses/i2c-omap.c > @@ -678,6 +678,8 @@ omap_i2c_rev1_isr(int this_irq, void *dev_id) > */ > static int errata_omap3_1p153(struct omap_i2c_dev *dev, u16 *stat, int *err) > { > + unsigned long timeout = jiffies + msecs_to_jiffies(1); > + > while (!(*stat & OMAP_I2C_STAT_XUDF)) { > if (*stat & (OMAP_I2C_STAT_NACK | OMAP_I2C_STAT_AL)) { > omap_i2c_ack_stat(dev, *stat & (OMAP_I2C_STAT_XRDY | > @@ -685,6 +687,12 @@ static int errata_omap3_1p153(struct omap_i2c_dev *dev, u16 *stat, int *err) > *err |= OMAP_I2C_STAT_XUDF; > return -ETIMEDOUT; > } > + > + if (time_after(jiffies, timeout)) { This is called from hard interrupt context, so we cannot use jiffies. > + dev_err(dev->dev, "timeout waiting on XUDF bit\n"); > + return 0; > + } > + > cpu_relax(); > *stat = omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG); > } A.