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
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