lkml.org 
[lkml]   [2013]   [Feb]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be)
Date
On Tuesday 05 February 2013 18:03:31 Alexey Brodkin wrote:
> The Xilinx System ACE Compact Flash chip is a true little-endian device
> and the PLB is a big-endian bus. Therefore the XPS System ACE Interface
> Controller will do a bit-swap in each byte when connecting the PLB data
> bus to the System ACE data bus as shown in Table 2.
>
> Note however, that the XPS System ACE Interface Controller does not
> perform the byte swapping necessary to interface to a little-endian
> device when configured to use 16-bit mode. Therefore, the software
> drivers provided for this core will perform the necessary byte-swapping
> to correctly interface to the Xilinx System ACE Compact Flash chip as
> shown in Table 3.

Ok. In this case, I would recommend making the default for this driver
little-endian, and adding a quirk for broken hardware bridges like the
one you cited to have a mixed-endian mode if configured so at compile
time.

It seems that on all normal platforms, this device should behave as
little-endian, while the Xilinx bridge can be either big-endian
or little-endian, depending on whether it is used in 8-bit or 16-bit
mode, so if we are using this, it cannot be known at compile time.

Arnd


\
 
 \ /
  Last update: 2013-02-05 16:43    [W:0.150 / U:9.656 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site