Linux 2.6.x : cpm_dpalloc alignment bug perhaps not fully r esolved

[Li Yang-r58472]

Did you apply the alignment patch too?  AFAIK, the problem is never fixed in 
mainstream trees.

Best Regards,
Leo
> -----Original Message-----
> From: linuxppc-embedded-bounces+leoli=freescale.com at ozlabs.org
> [mailto:linuxppc-embedded-bounces+leoli=freescale.com at ozlabs.org] On Behalf
> Of Laurent Lagrange
> Sent: Tuesday, July 04, 2006 11:37 PM
> To: pantelis at embeddedalley.com
> Cc: linuxppc-embedded at ozlabs.org
> Subject: Linux 2.6.x : cpm_dpalloc alignment bug perhaps not fully resolved
> 
> 
> Hello Pantelis,
> 
> Few months ago (25 January 2006), I sent a mail about an alignment bug in
> cpm_dpalloc.
> I applied and verified the provided patch. I was very satisfied with the
> result.
> 
> Today I port a driver from Linux 2.4 to Linux 2.6 and I have strange
> results.
> 
> The driver allocates rx and tx bds (8 bytes aligned) in the module_init for
> 4 SCC ports.
> That is always right. Then one port is opened by an application and a user
> configuration
> is set via an ioctl (set_conf).
> 
> This ioctl first frees the old bds :
> 	cpm_dpfree(chan->rx_bd_offset);
> 	cpm_dpfree(chan->tx_bd_offset);
> then allocates the new ones :
> 	chan->rx_bd_offset = cpm_dpalloc(sizeof(cbd_t) * chan->conf.rx_bufnbr,
> 8);
> 	chan->tx_bd_offset = cpm_dpalloc(sizeof(cbd_t) * chan->conf.tx_bufnbr,
> 8);
> with rx_bufnbr == 8 and tx_bufnbr == 2
> 
> module_init
> SCC1 rx_bd_offset=160
> SCC1 tx_bd_offset=1a8
> SCC2 rx_bd_offset=1c0
> SCC2 tx_bd_offset=208
> SCC3 rx_bd_offset=220
> SCC3 tx_bd_offset=260
> SCC4 rx_bd_offset=278
> SCC4 tx_bd_offset=2c0
> set_conf
> SCC1 rx_bd_offset=160
> SCC1 tx_bd_offset=1a4	-> ???
> 
> module_init
> SCC1 rx_bd_offset=160
> SCC1 tx_bd_offset=1a8
> SCC2 rx_bd_offset=1c0
> SCC2 tx_bd_offset=208
> SCC3 rx_bd_offset=220
> SCC3 tx_bd_offset=260
> SCC4 rx_bd_offset=278
> SCC4 tx_bd_offset=2c0
> set_conf
> SCC2 rx_bd_offset=1c0
> SCC2 tx_bd_offset=202	-> ???
> 
> module_init
> SCC1 rx_bd_offset=160
> SCC1 tx_bd_offset=1a8
> SCC2 rx_bd_offset=1c0
> SCC2 tx_bd_offset=208
> SCC3 rx_bd_offset=220
> SCC3 tx_bd_offset=260
> SCC4 rx_bd_offset=278
> SCC4 tx_bd_offset=2c0
> set_conf
> SCC3 rx_bd_offset=220
> SCC3 tx_bd_offset=260	-> ok
> 
> module_init
> SCC1 rx_bd_offset=160
> SCC1 tx_bd_offset=1a8
> SCC2 rx_bd_offset=1c0
> SCC2 tx_bd_offset=208
> SCC3 rx_bd_offset=220
> SCC3 tx_bd_offset=260
> SCC4 rx_bd_offset=278
> SCC4 tx_bd_offset=2c0
> set_conf
> SCC4 rx_bd_offset=278
> SCC4 tx_bd_offset=2c0	-> ok
> 
> WARNING : if I only uses the SCC1 port without allocating bds for the other
> ports,
> I can free and reallocate the bds for the SCC1 port as many times I want.
> 
> module_init
> SCC1 rx_bd_offset=160
> SCC1 tx_bd_offset=1a8
> set_conf
> SCC1 rx_bd_offset=160
> SCC1 tx_bd_offset=1a8	-> ok
> 
> Really, I don't understand how this can arise.
> Any idea ?
> 
> Thanks
> Laurent
> 
> 
> 
> 
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