David Daney wrote: > I am running the e100 driver on a MIPS 4KEc system (32 bit mips with > non-coherent DMA). There was a problem where received packets would > get 'stuck' for several seconds at a time and then be released all at > once. > > The cause was that if an interrupt were received when no RX packets > were available, the status for the receive buffer would be stuck in > the cache, so when the next interrupt arrived the old status value was > read (indicating no packets available) instead of the new value. > > The fix is to call pci_dma_sync_single_for_device on the RX if the > packet is not available to invalidate the cache so that at the next > interrupt valid status is returned. > > The driver currently calls pci_dma_sync_single_for_cpu before reading > the status, and this is indeed needed for cases like the R10000 CPU > where the cache can be polluted by speculative execution, but for most > machines it is a nop. > > The patch was tested on 2.6.17-rc4 on a MIPS 4KEc. > > Signed-off-by: David Daney <[EMAIL PROTECTED]> > --- > drivers/net/e100.c | 5 +++++ > 1 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/drivers/net/e100.c b/drivers/net/e100.c > index 19d32a2..fb8d551 100644 > --- a/drivers/net/e100.c > +++ b/drivers/net/e100.c > @@ -1840,6 +1840,11 @@ static int e100_rx_indicate(struct nic *nic, struct rx > *rx, > > if (readb(&nic->csr->scb.status) & rus_no_res) > nic->ru_running = RU_SUSPENDED; > + /* We are done looking at the buffer. Prepare it for > + * more DMA. */ > + pci_dma_sync_single_for_device(nic->pdev, rx->dma_addr, > + sizeof(struct rfd), > + PCI_DMA_FROMDEVICE); > return -ENODATA; > } > Should the call to pci_dma_sync_single_for_device be DMA_TO_DEVICE since we are giving the memory back to the device? -ack
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