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    SubjectRe: [PATCH] marvell sky2 driver: fix so it works without unaligned accesses
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    On Tue, 2012-04-03 at 11:13 -0400, Chris Metcalf wrote:
    > The driver uses a receive_new() routine that ends up requiring unaligned
    > accesses in IP header processing. If the architecture doesn't support
    > efficient unaligned accesses, just copy all ingress packets to the bounce
    > buffers instead.
    >
    > This allows the driver to be used on the Tilera TILEmpower-Gx, since
    > the tile architecture doesn't currently handle kernel unaligned accesses,
    > just userspace.
    >
    > Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
    > ---
    > drivers/net/ethernet/marvell/sky2.c | 10 +++++++---
    > 1 files changed, 7 insertions(+), 3 deletions(-)
    >
    > diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
    > index 879b0a4..7a15482 100644
    > --- a/drivers/net/ethernet/marvell/sky2.c
    > +++ b/drivers/net/ethernet/marvell/sky2.c
    > @@ -2490,6 +2490,7 @@ static struct sk_buff *receive_copy(struct sky2_port *sky2,
    > return skb;
    > }
    >
    > +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
    > /* Adjust length of skb with fragments to match received data */
    > static void skb_put_frags(struct sk_buff *skb, unsigned int hdr_space,
    > unsigned int length)
    > @@ -2555,6 +2556,7 @@ nomap:
    > nobuf:
    > return NULL;
    > }
    > +#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
    >
    > /*
    > * Receive one packet.
    > @@ -2598,10 +2600,12 @@ static struct sk_buff *sky2_receive(struct net_device *dev,
    > goto error;
    >
    > okay:
    > - if (length < copybreak)
    > - skb = receive_copy(sky2, re, length);
    > - else
    > +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
    > + if (length >= copybreak)
    > skb = receive_new(sky2, re, length);
    > + else
    > +#endif
    > + skb = receive_copy(sky2, re, length);
    >
    > dev->stats.rx_dropped += (skb == NULL);
    >

    The (expensive ?) copy should be done only if (sky2->hw->flags &
    SKY2_HW_RAM_BUFFER)
    diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
    index b806d9b..3da3cdc 100644
    --- a/drivers/net/ethernet/marvell/sky2.c
    +++ b/drivers/net/ethernet/marvell/sky2.c
    @@ -2599,7 +2599,11 @@ static struct sk_buff *sky2_receive(struct net_device *dev,
    goto error;

    okay:
    - if (length < copybreak)
    + if ((length < copybreak)
    +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
    + || (sky2->hw->flags & SKY2_HW_RAM_BUFFER)
    +#endif
    + )
    skb = receive_copy(sky2, re, length);
    else
    skb = receive_new(sky2, re, length);



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