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

From: Noralf TrÃnnes
Date: Wed Sep 28 2016 - 18:22:40 EST

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:

Should we put your note into the commit message?
It will most likely be lost if it just stays in this email.