On Tue, Sep 01, 2020 at 07:38:10PM +0200, Thomas Bogendoerfer wrote:
On Tue, Sep 01, 2020 at 07:16:27PM +0200, Christoph Hellwig wrote:
quoted
Well, if IP22 doesn't speculate (which I'm pretty sure is the case),
dma_sync_single_for_cpu should indeeed be a no-op. But then there
also shouldn't be anything in the cache, as the previous
dma_sync_single_for_device should have invalidated it. So it seems like
we are missing one (or more) ownership transfers to the device. I'll
try to look at the the ownership management in a little more detail
tomorrow.
this is the problem:
/* Always check for received packets. */
sgiseeq_rx(dev, sp, hregs, sregs);
so the driver will look at the rx descriptor on every interrupt, so
we cache the rx descriptor on the first interrupt and if there was
$no rx packet, we will only see it, if cache line gets flushed for
some other reason. kick_tx() does a busy loop checking tx descriptors,
with just sync_desc_cpu...
the patch below fixes the problem.
Thomas.
diff --git a/drivers/net/ethernet/seeq/sgiseeq.c b/drivers/net/ethernet/seeq/sgiseeq.c
index 8507ff242014..876e3700a0e4 100644
--- a/drivers/net/ethernet/seeq/sgiseeq.c
+++ b/drivers/net/ethernet/seeq/sgiseeq.c
@@ -112,14 +112,18 @@ struct sgiseeq_private {
static inline void dma_sync_desc_cpu(struct net_device *dev, void *addr)
{
- dma_cache_sync(dev->dev.parent, addr, sizeof(struct sgiseeq_rx_desc),
- DMA_FROM_DEVICE);
+ struct sgiseeq_private *sp = netdev_priv(dev);
+
+ dma_sync_single_for_device(dev->dev.parent, VIRT_TO_DMA(sp, addr),
+ sizeof(struct sgiseeq_rx_desc), DMA_FROM_DEVICE);
}
static inline void dma_sync_desc_dev(struct net_device *dev, void *addr)
{
- dma_cache_sync(dev->dev.parent, addr, sizeof(struct sgiseeq_rx_desc),
- DMA_TO_DEVICE);
+ struct sgiseeq_private *sp = netdev_priv(dev);
+
+ dma_sync_single_for_device(dev->dev.parent, VIRT_TO_DMA(sp, addr),
+ sizeof(struct sgiseeq_rx_desc), DMA_TO_DEVICE);
}
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
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