Re: [PATCH 2/2] omap i2c: add a timeout to the busy waiting

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Dec 17, 2009 at 08:38:39 +0530, Menon, Nishanth wrote:
> 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 <virtuoso@xxxxxxxxx>
> >CC: linux-i2c@xxxxxxxxxxxxxxx
> >CC: linux-omap@xxxxxxxxxxxxxxx
> >---
> > 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.

Well, I could calculate the timeout value based on current operating speed,
I guess. Or a delay. Perhaps OMAP_I2C_TIMEOUT can be used here?

> b) how did you arrive at the 10k iteration limit?

It was random, but then it seemed ok considering the l4 latency.

> > 		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
> --
> To unsubscribe from this list: send the line "unsubscribe linux-omap" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [Linux GPIO]     [Linux SPI]     [Linux Hardward Monitoring]     [LM Sensors]     [Linux USB Devel]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux