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

[Lucas Stach <l.stach@pengutronix.de>]

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.

------------------------>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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