Messages in this thread | | | Subject | Re: [PATCH 1/3] i2c: bcm2835: Fix hang for writing messages larger than 16 bytes | From | Noralf Trønnes <> | Date | Mon, 19 Sep 2016 19:36:23 +0200 |
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Den 19.09.2016 18:51, skrev Eric Anholt: > Noralf Trønnes <noralf@tronnes.org> writes: > >> Writing messages larger than the FIFO size results in a hang, rendering >> the machine unusable. This is because the RXD status flag is set on the >> first interrupt which results in bcm2835_drain_rxfifo() stealing bytes >> from the buffer. The controller continues to trigger interrupts waiting >> for the missing bytes, but bcm2835_fill_txfifo() has none to give. >> In this situation wait_for_completion_timeout() apparently is unable to >> stop the madness. >> >> The BCM2835 ARM Peripherals datasheet has this to say about the flags: >> TXD: is set when the FIFO has space for at least one byte of data. >> RXD: is set when the FIFO contains at least one byte of data. >> TXW: is set during a write transfer and the FIFO is less than full. >> RXR: is set during a read transfer and the FIFO is or more full. >> >> Implementing the logic from the downstream i2c-bcm2708 driver solved >> the hang problem. >> >> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> > Patches 1, 3 are: > > Reviewed-by: Eric Anholt <eric@anholt.net> > > For patch 2 I followed some of it, but couldn't quite say it's a review. > I trust your testing, and that the path has had a lot more testing in > the downstream tree, so it's:
I don't know how much testing downstream really has had since this feature is disabled by default. So there is a possibility that this can break some devices (while at the same time enable others). I wondered about adding a module parameter so it could be disabled at runtime, but decided to see what the review would be first. It is of course possible to add a this module parameter later should it turn out to break some device.
Noralf.
> Acked-by: Eric Anholt <eric@anholt.net> > > Thanks!
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