Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16with generic iowrite(read)8/16(be)

[Grant Likely]

On Tue, Feb 5, 2013 at 3:12 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> 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.

The driver already handles this. It has three sets of accessors;
8-bit, 16-bit LE and 16-bit BE *and* when doing 16-bit it figures out
on its own which set to use at runtime. There is nothing controversial
here. The only problem is that the driver is currently using in_/out_
IO accessors instead of ioread/iowrite variants.

g.
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