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SubjectRe: [PATCH V2] i2c: designware: fix race between subsequent xfers
On Fri, Jun 14, 2013 at 04:37:41PM +0200, Wolfram Sang wrote:
> On Fri, Jun 07, 2013 at 10:51:23AM +0200, Christian Ruppert wrote:
> > The designware block is not always properly disabled in the case of
> > transfer errors. Interrupts from aborted transfers might be handled
> > after the data structures for the following transfer are initialised but
> > before the hardware is set up. This can corrupt the data structures to
> > the point that the system is stuck in an infinite interrupt loop (where
> > FIFOs are never emptied because dev->msg_read_idx == dev->msgs_num).
> >
> > This patch cleanly disables the designware-i2c hardware at the end of
> > every transfer, be it successful or not.
> >
> > This patch requires https://patchwork.kernel.org/patch/2601241/ to be
> > applied first.
>
> These last two lines should be below "---".
>
> >
> > Signed-off-by: Christian Ruppert <christian.ruppert@abilis.com>
> > ---
> > drivers/i2c/busses/i2c-designware-core.c | 10 ++++++++--
> > 1 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
> > index b75d292..55a9991 100644
> > --- a/drivers/i2c/busses/i2c-designware-core.c
> > +++ b/drivers/i2c/busses/i2c-designware-core.c
> > @@ -588,11 +588,19 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
> > ret = wait_for_completion_timeout(&dev->cmd_complete, HZ);
> > if (ret == 0) {
> > dev_err(dev->dev, "controller timed out\n");
> > + /* i2c_dw_init implicitly disables the adapter */
> > i2c_dw_init(dev);
> > ret = -ETIMEDOUT;
> > goto done;
> > }
> >
> > + /*
> > + * We must disable the adapter before unlocking the &dev->lock mutex
> > + * below. Otherwise the hardware might continue generating interrupts
> > + * which in turn causes a race condition with the following transfer.
>
> I added "Needs some more investigation if the additional interrupts are
> a hardware bug or this driver doesn't handle them correctly yet." to the
> comment and
>
> Applied to for-next, thanks!

Sorry for the late response (was on vacation). This patch looks good to me
as well. Thanks for applying it!


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