[U-Boot] [linux-sunxi] Uboot error: address not aligned in v7_dcache_inval_range

[Marek Vasut <marex@denx.de>]

On Saturday, April 19, 2014 at 03:30:14 PM, Ian Campbell wrote:
> On Sun, 2014-04-13 at 23:45 -0400, Shixin Zeng wrote:
> > Hi,
> > 
> > I compiled the current u-boot from
> > https://github.com/jwrdegoede/u-boot-sunxi.git for cubieboard2, and
> > wrote it to the SD card. I was trying to boot the kernel on my
> > computer over network by tftp, however it failed when I ran "dhcp" or
> > "tftp" command in uboot with a tons of:
> > 
> > 
> > ERROR: v7_dcache_inval_range - start address is not aligned - 0x7fb677e0
> > ERROR: v7_dcache_inval_range - stop address is not aligned - 0x7fb67820
> 
> I'm seeing this on Cubieboard2 and Cubietruck. It appears to be down to
> a change to the upstream designware driver:
> 
> commit 50b0df814b0f75c08a3d45a017016a75af3edb5d
> Author: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
> Date:   Wed Jan 22 20:49:09 2014 +0400
> 
>     net/designware: make driver compatible with data cache
> 
>     Up until now this driver only worked with data cache disabled.
>     To make it work with enabled data cache following changes were
> required:
> 
>      * Flush Tx/Rx buffer descriptors their modification
>      * Invalidate Tx/Rx buffer descriptors before reading its values
>      * Flush cache for data passed from CPU to GMAC
>      * Invalidate cache for data passed from GMAC to CPU
> 
> http://git.denx.de/?p=u-boot.git;a=commit;h=50b0df814b0f75c08a3d45a017016a7
> 5af3edb5d
> 
> I suppose this was only tested on some architecture which allows DMA
> flush/invaidation at a fairly fine granularity (at least down to 4 byte
> boundaries)

This was a sheer luck this ever worked. Looking at the entire driver, to fix all 
your issues with DMA and caches, it would be sufficient to re-align "struct 
dw_eth_dev" properly.

See drivers/net/designware.h:
1) struct dmamacdescr {} is already __aligned(ARCH_DMA_MINALIGN)
   => This structure, if aligned in memory to proper boundary, can be flushed/
      invalidated without problems.
2) struct dw_eth_dev {} can be aligned to ANY 4-byte boundary
   But this structure contains two arrays of struct dmamacdescr {} , which each
   have their elements' lenght aligned to ARCH_DMA_MINALIGN

Solution:

Your patch [1/3] and reorder the structure in designware.h so that the
struct dmamacdescr tx_mac_descrtable[]
struct dmamacdescr rx_mac_descrtable[]
are first and anything that does not need to be aligned follows. This way, the 
DMA descriptors will always be aligned and you need not worry about the flushes. 
You don't even need to ROUNDUP their length, since they are already fine.

When reordering the struct dw_eth_dev {}, make sure to add a comment about the 
alignment.

Best regards,
Marek Vasut