[PATCH] B43: Handle DMA RX descriptor underrun

[Michael Büsch]

On Sun, 5 May 2013 14:44:14 +0200
Rafał Miłecki <zajec5 at gmail.com> wrote:

> 2013/4/23 Thommy Jakobsson <thommyj at gmail.com>:
> > Add handling of rx descriptor underflow. This fixes a fault that could
> > happen on slow machines, where data is received faster than the CPU can
> > handle. In such a case the device will use up all rx descriptors and
> > refuse to send any more data before confirming that it is ok. This
> > patch enables necessary interrupt to discover such a situation and will
> > handle them by dropping everything in the ring buffer.
> 
> Thommy: does it mean firmware actually ignores what we write to the
> B43_DMA64_RXINDEX (recently renamed to the B43_DMA64_RXSTOPINDEX)? Is
> our set_current_rxslot and op64_set_current_rxslot (same for 32bit
> version) useless in this situation?
> 
> Could this be a off-by-one issue? Maybe we're writing a value too low
> by a one and firmware believes the whole ring is empty while it's
> full?

The ring looks the same if it's full or empty. We can only know that it is
full when this interrupt fires, which happens as the indexes collide.

-- 
Michael
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