[U-Boot] [PATCH v2] drivers/net/designware - fix alignment of buffer descriptors

[Vipin Kumar <vipin.kumar@st.com>]

On 9/25/2013 8:57 PM, Alexey Brodkin wrote:
> It's important that buffer descriptors are aligned in accordance to GMAC
> data bus width (32/64/128-bit). It's safe to align to 128-bit (16-bytes)
> for every bus width type.
>
> If buffer descriptor is improperly aligned GMAC discards lower bits of
> provided address and as a result reads from improper location that
> doesn't match expected fields.
>
> Commit ef76025a99247cdb8f927a2c9f15400678dfb599 "net: Multiple
> updates/enhancements to designware.c" introduced another structure
> member "link_printed" right before buffer descriptors while "padding"
> member was left untouched. This together with alignment of structure
> itself to 16-byte boundary forces buffer descriptoprs always to be
> 4-byte aligned that causes driver complete disfunction if GMAC bus width
> is 64 or 128-bit.
>

I have also faced this problem before. May be a better solution is to 
place all the struct and buffer declarations at the very start of 
dw_eth_dev structure (off-course with a comment that these should not be 
moved). It may avoid the problem in later modifications

Regards
Vipin