From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Metcalf Subject: Re: [PATCH v2] marvell sky2 driver: fix so it works without unaligned accesses Date: Wed, 4 Apr 2012 17:52:44 -0400 Message-ID: <4F7CC2AC.5040309@tilera.com> 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> <20120404114253.5f84d4c8@s6510.linuxnetplumber.net> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: David Miller , , To: Stephen Hemminger Return-path: In-Reply-To: <20120404114253.5f84d4c8@s6510.linuxnetplumber.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 4/4/2012 2:42 PM, Stephen Hemminger wrote: > 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); Acked-by: Chris Metcalf This works on our TILEmpower-Gx boxes and seems like it's likely more efficient. I believe kernel style says you should "return true" rather than "return 1" from a "bool" routine, though. Thanks! -- Chris Metcalf, Tilera Corp. http://www.tilera.com