From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH v2] marvell sky2 driver: fix so it works without unaligned accesses Date: Wed, 4 Apr 2012 11:42:53 -0700 Message-ID: <20120404114253.5f84d4c8@s6510.linuxnetplumber.net> References: <20120403.174610.2089715131687430500.davem@davemloft.net> <1333469916.18626.284.camel@edumazet-glaptop> <201204031527.q33FR04i031747@farm-0027.internal.tilera.com> <201204041419.q34EJ49H025297@farm-0012.internal.tilera.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: David Miller , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Chris Metcalf Return-path: In-Reply-To: <201204041419.q34EJ49H025297@farm-0012.internal.tilera.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, 4 Apr 2012 10:13:32 -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, and SKY2_HW_RAM_BUFFER is set, > just copy all ingress packets to the bounce buffers instead. > Thanks to Eric Dumazet for pointing out the SKY2_HW_RAM_BUFFER issue. > > 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 > --- > drivers/net/ethernet/marvell/sky2.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) What about the following (compile tested only) --- a/drivers/net/ethernet/marvell/sky2.c 2012-04-04 08:49:05.954853108 -0700 +++ b/drivers/net/ethernet/marvell/sky2.c 2012-04-04 11:30:54.201432707 -0700 @@ -2468,6 +2468,17 @@ static int sky2_change_mtu(struct net_de return err; } +static inline bool needs_copy(const struct rx_ring_info *re, + unsigned length) +{ +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS + /* Some architectures need the IP header to be aligned */ + if (!IS_ALIGNED(re->data_addr + ETH_HLEN, sizeof(u32))) + return 1; +#endif + return length < copybreak; +} + /* For small just reuse existing skb for next receive */ static struct sk_buff *receive_copy(struct sky2_port *sky2, const struct rx_ring_info *re, @@ -2605,7 +2616,7 @@ static struct sk_buff *sky2_receive(stru goto error; okay: - if (length < copybreak) + if (needs_copy(re, length)) skb = receive_copy(sky2, re, length); else skb = receive_new(sky2, re, length);