> -----Original Message-----
> From: Marek Vasut <marex@xxxxxxx>
> Sent: Monday, June 29, 2020 5:11 AM
> To: Raviteja Narayanam <rna@xxxxxxxxxx>; linux-i2c@xxxxxxxxxxxxxxx
> Cc: Michal Simek <michals@xxxxxxxxxx>; Shubhrajyoti Datta
> <shubhraj@xxxxxxxxxx>; Wolfram Sang <wsa@xxxxxxxxxx>
> Subject: Re: [PATCH 4/5] i2c: xiic: Switch from waitqueue to completion
>
> On 6/26/20 2:13 PM, Raviteja Narayanam wrote:
>
> Hi,
>
> [...]
>
> >> @@ -703,23 +704,24 @@ static int xiic_xfer(struct i2c_adapter *adap,
> >> struct i2c_msg *msgs, int num)
> >> err = xiic_start_xfer(i2c, msgs, num);
> >> if (err < 0) {
> >> dev_err(adap->dev.parent, "Error xiic_start_xfer\n");
> >> - goto out;
> >> + return err;
> >> }
> >>
> >> - if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
> >> - (i2c->state == STATE_DONE), HZ)) {
> >> - mutex_lock(&i2c->lock);
> >> - err = (i2c->state == STATE_DONE) ? num : -EIO;
> >> - goto out;
> >> - } else {
> >> - mutex_lock(&i2c->lock);
> >> + err = wait_for_completion_interruptible_timeout(&i2c->completion,
> >> + XIIC_I2C_TIMEOUT);
> >
> > This is causing random lock up of bus. Since it is "interruptible"
> > API, once we enter Ctrl+C, It is coming out of wait state, the message
> pointers are made NULL and the ongoing transaction is not completed.
> > Can use " wait_for_completion_timeout" API in place of this.
> >
> >> + mutex_lock(&i2c->lock);
>
> So in case this is interrupted, we would have to somehow reset the controller ?
Yes, but the cleanup is not straight forward because we do not know the exact state
Of controller and the I2C bus. That’s why preferring a non-interruptible API.
> What sort of lockups do you see exactly ?
There is an i2ctransfer going on (let's say a read of 255 bytes), we get interrupt everytime the Rx FIFO is full.
While the controller is receiving data, if there is a signal, this is exiting abruptly and there is no STOP condition
on the bus. So, no master can communicate on that bus further.
Can you share some sort of test case,
> so I can replicate it ?
I have 3 scripts running with commands like below, and I am randomly giving Ctrl+C.
i=0
while [ 1 ]
do
i2ctransfer -y -f 0 w1@0X54 0X00 r255@0X54
i=$(expr $i + 1)
echo "$i"
done
>
> Thanks
>
> [...]
Raviteja N
