[PATCH v1 2/8] spi: dw: Add device tree properties for fields in CTRL0

[Sean Anderson <seanga2@gmail.com>]

On 3/21/20 9:51 PM, Marek Vasut wrote:
> On 3/5/20 8:19 PM, Sean Anderson wrote:
>> Some devices have different layouts for the fields in CTRL0 (e.g. the
>> Kendryte K210). Allow this layout to be configurable from the device tree.
>> The documentation has been taken from Linux.
>>
>> Signed-off-by: Sean Anderson <seanga2@gmail.com>
>> Reviewed-by: Simon Glass <sjg@chromium.org>
> 
> Can't you just have different compatible string for each SoC and derive
> the various fields based on that compatible string, instead of
> describing all the register bitfields in DT ?
> 
> What does Linux do ?
> 

Linux only supports socfpga boards. I don't know if there is any
rhyme/reason to the shifting around of these fields. It is possible to
add several compatible strings like "kendryte,k210-spi3". I chose this
method because the bitfields are different for spi0 and spi1, spi2, and
spi3. If there are other incompatibilities discovered, then it may make
more sense to use different strings. Another option could have been to
use the DW_SPI_VERSION field to detect different controllers, but it is
the same among all the controllers on the K210. 

--Sean