On 02/10/2011 06:48 PM, Christian Lamparter wrote:
> Documentation/DMA-API-HOWTO.txt states:
>
> "DMA transfers need to be synced properly in order for
> the cpu and device to see the most uptodate and correct
> copy of the DMA buffer."
>
> Cc: <stable@xxxxxxxxxx>
> Signed-off-by: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx>
> ---
> Embarrassingly, this bug is unique to p54 and has been around
> since 2.6.25. This tells us something interesting about our
> userbase.
I do use it on a LE system that probably has coherent DMA. Did someone run into
this bug?
> ---
> diff --git a/drivers/net/wireless/p54/p54pci.c b/drivers/net/wireless/p54/p54pci.c
> index 1eacba4..0494d7b 100644
> --- a/drivers/net/wireless/p54/p54pci.c
> +++ b/drivers/net/wireless/p54/p54pci.c
> @@ -199,6 +199,7 @@ static void p54p_check_rx_ring(struct ieee80211_hw *dev, u32 *index,
> while (i != idx) {
> u16 len;
> struct sk_buff *skb;
> + dma_addr_t dma_addr;
> desc = &ring[i];
> len = le16_to_cpu(desc->len);
> skb = rx_buf[i];
> @@ -216,17 +217,20 @@ static void p54p_check_rx_ring(struct ieee80211_hw *dev, u32 *index,
>
> len = priv->common.rx_mtu;
> }
> + dma_addr = le32_to_cpu(desc->host_addr);
> + pci_dma_sync_single_for_cpu(priv->pdev, dma_addr,
> + priv->common.rx_mtu + 32, PCI_DMA_FROMDEVICE);
> skb_put(skb, len);
>
> if (p54_rx(dev, skb)) {
> - pci_unmap_single(priv->pdev,
> - le32_to_cpu(desc->host_addr),
> - priv->common.rx_mtu + 32,
> - PCI_DMA_FROMDEVICE);
> + pci_unmap_single(priv->pdev, dma_addr,
> + priv->common.rx_mtu + 32, PCI_DMA_FROMDEVICE);
> rx_buf[i] = NULL;
> - desc->host_addr = 0;
> + desc->host_addr = cpu_to_le32(0);
How does a BE zero differ from a LE zero? Using it this way emphasizes that it
needs to be translated - I'm not objecting, just curious.
Larry
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