(resending with some corrections after original email bounced) Hi all,
I tested original version of this patch and it happen to fix the issue on Linksys WRT54GL (based on Broadcom 5352 SoC). However I think that the bug is still present. After closer look it seems that DMA buffers may be used incorrectly in b43_dma_rx. I don't have documentation for Broadcom WLAN chipsets, but DMA engine used by for BCM440X apparently has similar design. Looking at "RECEIVE DESCRIPTOR TABLE POINTER REGISTER" (page 35 of http://www.broadcom.com/collateral/pg/440X-PG02-R.pdf), B43_DMA32_RXINDEX should be left pointing after last valid descriptor as initialized in dmacontroller_setup. Notice that the last valid descriptor already has B43_DMA32_DCTL_DTABLEEND set, so DMA should operate in a round-robin fashion. B43_DMA32_RXINDEX is reprogrammed from b43_dma_rx, by calling ops->set_current_rxslot(ring, slot). The patch from Thommy simply reprogrammes the register back with the same value as initialized in dmacontroller_setup. I suspect that with set_current_rxslot call removed, the patch from Thommy will not be necessary anymore. I'm currently testing such fix and will report back in a few days. Regards, Piotr On Sat, Apr 20, 2013 at 9:16 PM, Thommy Jakobsson <thom...@gmail.com> wrote: > > > On Sat, 20 Apr 2013, Michael Büsch wrote: > >> On Sat, 20 Apr 2013 21:47:10 +0200 (CEST) >> Thommy Jakobsson <thom...@gmail.com> wrote: >> >> > > And I think you need to set ring->current_slot to the value of >> > > ring->ops->get_current_slot(). >> > > Not 100% sure, though, since it is years since I worked on that code. >> > > >> > Is that really needed? They should already be the same since the device >> > has thrown the underflow interrupt >> >> Hm not sure. But should be easy to verify. > I did check it in the beginning when I was testing the patch, just printed > the indexes in the kernel log. But of course if there is a race condition > it could be hard to catch. Have used the patch for several weeks > and several 100Gb now, so it does seem to work. > > The reason for getting this interrupt is that the current descriptor > pointer (RXDPTR) has the same value as the descriptor index (RXINDEX). The > descriptor index is set at the end of b43_dma_rx with > ops->set_current_rxslot. At the next line, and with the same value, the > ring->current slot is set. So in my opinion I don't need to set it. But I > could have missed something. > > BR, > Thommy > _______________________________________________ > b43-dev mailing list > b43-dev@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/b43-dev > _______________________________________________ b43-dev mailing list b43-dev@lists.infradead.org http://lists.infradead.org/mailman/listinfo/b43-dev
