[PATCH 2/2] spi: imx: fix use of native chip-selects with devicetree

[Greg Ungerer]

On 21/03/17 18:05, Uwe Kleine-König wrote:
> On Tue, Mar 21, 2017 at 12:05:20PM +1000, Greg Ungerer wrote:
>> On 20/03/17 23:22, Vladimir Zapolskiy wrote:
>>> For that type of bindings locally I have a hackish spi-imx driver change,
>>> which supports this option, but I'm unsure if it is universal enough.
>>
>> Do you mean supporting no cs-gpios tag?
>> That would be nice, but it would seem not many users of this are
>> using native chip selects.
>
> The reason for this is that the native chip selects are less flexible
> than gpios because you cannot control when they deassert. IIRC they do
> it too much for some chips. So the only reason to stick to them is that
> on some SoCs not all pins have a GPIO function. Not sure if transfer
> speed is another reason, but I would expect that the gain isn't that
> big.

For the particular SPI device I am using, a Silicon Labs 32260,
it actually wants the assertion and de-assertion of the chip-select
between each byte. So it is the only way it can work for me.

Regards
Greg