Re: [PATCH] net: cpsw: invalidate complete buffer

[Jan Weitzel <J.Weitzel@phytec.de>]

On Fri, Feb 27, 2015 at 02:45:18PM +0100, Lucas Stach wrote:
> Am Freitag, den 27.02.2015, 14:39 +0100 schrieb Lucas Stach:
> > Am Freitag, den 27.02.2015, 14:14 +0100 schrieb Jan Weitzel:
> > > On Fri, Feb 27, 2015 at 12:47:24PM +0100, Lucas Stach wrote:
> > > > Am Freitag, den 27.02.2015, 10:56 +0100 schrieb Jan Weitzel:
> > > > > Without invalidating the complete buffer before giving it to
> > > > > dma_inv_range, we got strange packets.
> > > > > 
> > > > 
> > > > This is most likely not the correct fix. If this helps then our
> > > > dma_inv_range functions aren't working properly, which would be really
> > > > bad. How do those "strange packets" look like?
> > > > 
> > > We saw the problem with tftp transfers of a 76 byte image. Debug print in
> > > tftp_handler
> > > 
> > > good:
> > > tftp_handler: len:76 blocksize:1432 to fifo
> > > 00000000: 06 08 ba de 7d 27 e1 2c 52 2f cf 77 e0 d3 23 da    ....}'.,R/.w..#.
> > > 00000010: 62 d4 42 3e 03 20 3a c2 51 aa 51 15 73 be 9e 21    b.B>. :.Q.Q.s..!
> > > 00000020: 03 ac 78 a9 e3 4f cd 4d 6d ba 93 fe 83 dc fe 82    ..x..O.Mm.......                                                         
> > > 00000030: bb f8 24 29 6e 6f 53 1c 91 52 4b 77 1b 72 ff a0    ..$)noS..RKw.r..                                                         
> > > 00000040: 5b 98 1c 20 28 09 0f 4c 93 3c 22 08                [.. (..L.<".     
> > > 
> > > bad:
> > > tftp_handler: len:76 blocksize:1432 to fifo:                                                                                          
> > > 00000000: 06 08 ba de 7d 27 e1 2c 52 2f cf 77 e0 d3 23 da    ....}'.,R/.w..#.                                                         
> > > 00000010: 62 d4 6b 73 69 7a 65 00 31 34 33 32 00 b0 1b d1    b.ksize.1432....                                                         
> > > 00000020: 5b d4 78 a9 e3 4f cd 4d 6d ba 93 fe 83 dc fe 82    [.x..O.Mm.......
> > > 00000030: bb f8 24 29 6e 6f 53 1c 91 52 4b 77 1b 72 ff a0    ..$)noS..RKw.r..
> > > 00000040: 5b 98 1c 20 28 09 0f 4c 93 3c 22 08                [.. (..L.<".
> > > 
> > > 
> > > The ethernet package has 122 Bytes and the error in the received file is on
> > > offset 18. The data "b.ksize.1432" comes also from tftp packets.
> > > 
> > This doesn't look like a problem to invalidate the cache, but more like
> > writeback of old cachelines while the hardware owns the buffer. Can you
> > try the series "Phasing out direct usage of asm/mmu.h on ARM" and see if
> > this still happens there? If I'm correct this series should fix this
> > problem.
> > 
> > I'll send an updated version of this series in the evening, but you
> > should be able to correct the typo in cpsw.c yourself for testing. :)
> 
> Or try this patch, which should do the same as the new cache handling,
> but may be acceptable for master.
Your patch works and invalidating after reading makes sense ;)
Can we take this for master? I'll test the series.

Tested-by: Jan Weitzel <j.weitzel@phytec.de>

> 
> ------------------------>8--------------------------------------------
> From f96aec8bd87ac29247617bdcfab41048b942e899 Mon Sep 17 00:00:00 2001
> From: Lucas Stach <l.stach@pengutronix.de>
> Date: Fri, 27 Feb 2015 14:41:46 +0100
> Subject: [PATCH] net: cpsw: prevent stray cache writeback
> 
> The cache should be invalidated when transfering ownership of a buffer
> to the device. Otherwise the writeback of dirty cache lines can
> corrupt the hardware written data.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  drivers/net/cpsw.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/cpsw.c b/drivers/net/cpsw.c
> index 799fac89a2f3..301b8a9dfde5 100644
> --- a/drivers/net/cpsw.c
> +++ b/drivers/net/cpsw.c
> @@ -888,6 +888,7 @@ static int cpsw_recv(struct eth_device *edev)
>  	while (cpdma_process(priv, &priv->rx_chan, &buffer, &len) >= 0) {
>  		dma_inv_range((ulong)buffer, (ulong)buffer + len);
>  		net_receive(edev, buffer, len);
> +		dma_inv_range((ulong)buffer, (ulong)buffer + len);
>  		cpdma_submit(priv, &priv->rx_chan, buffer, PKTSIZE);
>  	}
>  
> -- 
> 2.1.4
> -- 
> Pengutronix e.K.             | Lucas Stach                 |
> Industrial Linux Solutions   | http://www.pengutronix.de/  |
> 

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