Re: [PATCH v3 2/7] i2c: bcm2835: Protect against unexpected TXW/RXR interrupts

[Noralf TrÃnnes]

Den 29.09.2016 07:37, skrev Stefan Wahren:
> > Noralf TrÃnnes <noralf@xxxxxxxxxxx> hat am 29. September 2016 um 00:22
> > geschrieben:
> >
> >
> >
> > Den 29.09.2016 00:00, skrev Eric Anholt:
> > > Noralf TrÃnnes <noralf@xxxxxxxxxxx> writes:
> > >
> > > > If an unexpected TXW or RXR interrupt occurs (msg_buf_remaining == 0),
> > > > the driver has no way to fill/drain the FIFO to stop the interrupts.
> > > > In this case the controller has to be disabled and the transfer
> > > > completed to avoid hang.
> > > >
> > > > (CLKT | ERR) and DONE interrupts are completed in their own paths, and
> > > > the controller is disabled in the transfer function after completion.
> > > > Unite the code paths and do disabling inside the interrupt routine.
> > > >
> > > > Clear interrupt status bits in the united completion path instead of
> > > > trying to do it on every interrupt which isn't necessary.
> > > > Only CLKT, ERR and DONE can be cleared that way.
> > > >
> > > > Add the status value to the error value in case of TXW/RXR errors to
> > > > distinguish them from the other S_LEN error.
> > > I was surprised that not writing the TXW/RXR bits on handling their
> > > interrupts was OK, given that we were doing so before, but it's a level
> > > interrupt and those bits are basically ignored on write.
> > >
> > > This patch and 3, 4, and 6 are:
> > >
> > > Reviewed-by: Eric Anholt <eric@xxxxxxxxxx>
> > >
> > > Patch 5 is:
> > >
> > > Acked-by: Eric Anholt <eric@xxxxxxxxxx>
> > >
> > > Note for future debug: The I2C_C_CLEAR on errors will take some time to
> > > resolve -- if you were in non-idle state and I2C_C_READ, it sets an
> > > abort_rx flag and runs through the state machine to send a NACK and a
> > > STOP, I think.  Since we're setting CLEAR without I2CEN, that NACK will
> > > be hanging around queued up for next time we start the engine.
> > Maybe you're able to explain the issues I had with reset:
> > https://github.com/raspberrypi/linux/issues/1653
> >
> > Should we put your note into the commit message?
> > It will most likely be lost if it just stays in this email.
> I prefer to have this kind of information as a code comment.

Eric, does this look good to you as a code comment:

/*
 * Note about I2C_C_CLEAR on error:
 * The I2C_C_CLEAR on errors will take some time to resolve -- if you 
were in
 * non-idle state and I2C_C_READ, it sets an abort_rx flag and runs through
 * the state machine to send a NACK and a STOP. Since we're setting CLEAR
 * without I2CEN, that NACK will be hanging around queued up for next time
 * we start the engine.
 */


If it is, I'll resend the series with this change and add all the ack's 
and r-b's.

Noralf.