From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Menon, Nishanth" Subject: Re: [PATCH 2/2] omap i2c: add a timeout to the busy waiting Date: Thu, 17 Dec 2009 08:38:39 +0530 Message-ID: <4B29A0B7.1020908@ti.com> References: <1260972144-31593-1-git-send-email-virtuoso@slind.org> <1260972144-31593-2-git-send-email-virtuoso@slind.org> <1260972144-31593-3-git-send-email-virtuoso@slind.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1260972144-31593-3-git-send-email-virtuoso@slind.org> Sender: linux-omap-owner@vger.kernel.org To: Alexander Shishkin Cc: "ben-linux@fluff.org" , "linux-omap@vger.kernel.org" , "linux-i2c@vger.kernel.org" List-Id: linux-i2c@vger.kernel.org Alexander Shishkin said the following on 12/16/2009 07:32 PM: > 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 > CC: linux-i2c@vger.kernel.org > CC: linux-omap@vger.kernel.org > --- > drivers/i2c/busses/i2c-omap.c | 7 ++++++- > 1 files changed, 6 insertions(+), 1 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > index ad8242a..b474c20 100644 > --- a/drivers/i2c/busses/i2c-omap.c > +++ b/drivers/i2c/busses/i2c-omap.c > @@ -678,7 +678,9 @@ omap_i2c_rev1_isr(int this_irq, void *dev_id) > */ > static int omap3430_workaround(struct omap_i2c_dev *dev, u16 *stat, int *err) > { > - while (!(*stat & OMAP_I2C_STAT_XUDF)) { > + unsigned long timeout = 10000; > + > + while (!(*stat & OMAP_I2C_STAT_XUDF && --timeout)) { > a) timeout without using an actual delay is not a good idea - consider each OPP - we can go upto 1ghz on 3630, the actual time for 10000 iterations will depend on the MPU speed. b) how did you arrive at the 10k iteration limit? > if (*stat & (OMAP_I2C_STAT_NACK | OMAP_I2C_STAT_AL)) { > omap_i2c_ack_stat(dev, *stat & (OMAP_I2C_STAT_XRDY | > OMAP_I2C_STAT_XDR)); > @@ -689,6 +691,9 @@ static int omap3430_workaround(struct omap_i2c_dev *dev, u16 *stat, int *err) > *stat = omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG); > } > > + if (!timeout) > + dev_err(dev->dev, "timeout waiting on XUDF bit\n"); > + > return 0; > } > > Regards, Nishanth Menon