Re: [PATCH 2/2] spi: spi-mem: fallback to using transfers when CS gpios are used

[Conor Dooley <conor@kernel.org>]

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On Thu, Nov 07, 2019 at 05:42:35PM +1300, Chris Packham wrote:
> Devices with chip selects driven via GPIO are not compatible with the
> spi-mem operations. Fallback to using standard spi transfers when the
> device is connected with a gpio CS.

Bitta necromancy, but why are they not compatible?
Couldn't you have just done an if/else in your driver to call
gpiod_set_value(spi_get_csgpiod())?

For some context, I've been trying to resolve some issues with using
the standard transfers code when used with flash devices in the
microchip-core-qspi driver, but if I delete this !mem->spi->cs_gpiod
check, and add the aforementioned if/else in my driver, the mem ops
work fine.

What am I missing that makes them incompatible?

Cheers,
Conor.

> 
> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> ---
>  drivers/spi/spi-mem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 9f0fa9f3116d..e5a46f0eb93b 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -286,7 +286,7 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
>  	if (!spi_mem_internal_supports_op(mem, op))
>  		return -ENOTSUPP;
>  
> -	if (ctlr->mem_ops) {
> +	if (ctlr->mem_ops && !mem->spi->cs_gpiod) {
>  		ret = spi_mem_access_start(mem);
>  		if (ret)
>  			return ret;
> -- 
> 2.24.0
> 

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