Re: Bug: mv643xxx fails with highmem

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Thu, Dec 11, 2014 at 03:10:55PM -0500, David Miller wrote:
> From: Russell King - ARM Linux <linux@arm.linux.org.uk>
> Date: Thu, 11 Dec 2014 19:49:20 +0000
> 
> > Commit 69ad0dd7af22 removed skb_frag_dma_map() in favour of mapping
> > all fragments with dma_map_single().  This fails when the driver is
> > used in an environment with highmem.
> 
> This change looks really buggy to me.
> 
> Unfortunately, all the changes he subsequently makes for software TSO
> support depend upon this :-/
> 
> The change is definitely wrong.

Thanks for confirming where the bug is.

Would other drivers need fixing for this as well?  Eg, fec_main.c
does the following, and this driver is used on iMX6 which can also have
highmem:

static int
fec_enet_txq_submit_frag_skb(struct fec_enet_priv_tx_q *txq,
                             struct sk_buff *skb,
                             struct net_device *ndev)
{
                bufaddr = page_address(this_frag->page.p) + this_frag->page_offset;
...
                addr = dma_map_single(&fep->pdev->dev, bufaddr, frag_len,
                                      DMA_TO_DEVICE);

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