Hi Stefan,
On 26/10/2016 23:51, Stefan Schmidt wrote:
Hello.
On 27/10/16 00:33, Stefan Schmidt wrote:
Hello.
On 25/10/16 18:36, Harry Morris wrote:
Hi Stefan,
On 25/10/2016 16:54, Stefan Schmidt wrote:
Start should with a capital S here as you do on all other lines. Total
nitpick. :)
Perfect, I'm sure there's a few more elsewhere I've missed
+ - reg: Controlling chip select
+ - spi-max-frequency: Maximum clock speed, should be *less
than*
+ 4000000
+ - spi-cpol: Invert clock polarity
Is this a mandatory field for the bindings? I would expect one being
the default and used while the other one being an optional property
and only used when the hardware setup needs this. Does this make
sense?
I'm afraid not, my understanding is that the spi-cpol property is used
by the spi master driver rather than the device driver, so if I need
CPOL=1 (which the CA8210 always does) then the user doesn't have a
choice but to specify spi-cpol here? As omitting would cause the spi
master to use CPOL=0 for the attached slave.
I would expect there is a way to set this in the driver itself as it is
the default and the only working mode. Having to set it in the device
tree bindings seems odd as this is really no option or parameter that
can be changed.
Did you look around in other SPI driver so see how they handle such a
situation?
I did look around myself quickly and it seems indeed the way to set
the clock polarity. Just keep it. Maybe adjust the description to
"Requires invert clock polarity".
I'm not sure which is the "correct" approach but I think you're right
actually, I can indeed set the mode in the spi_device struct from the
driver, eliminating the need to invert the polarity in the device tree.
Since the mode is fixed for the hardware I agree it makes more sense to
set it in the driver rather than the device tree. I'm happy to make the
change.
Thanks,
Harry
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