[PATCH] spi: spi-mem: ease checks in dtr_supports_op()

[Dhruva Gole]

Forgot to add in CC,
+ Jagan Teki <jagan at amarulasolutions.com> (maintainer:SPI)

On 20/10/22 14:04, Dhruva Gole wrote:
> Remove the extra conditions that cause some cases to fail prematurely
> like if the data number of bytes is odd. The controller can handle odd
> number of bytes data read in DTR Mode. Don't fail supports op for this
> condition.
> 
> Signed-off-by: Dhruva Gole <d-gole at ti.com>
> ---
> 
> For a deeper context, refer to a cover letter from an earlier patch
> series:
> https://lore.kernel.org/u-boot/20221019064759.493607-1-d-gole@ti.com/T/#m3fd93bdcc30b3b5faada6abe45a4104388afc300
> Here, I am trying to boot from OSPI Flash present on board the AM62-SK
> EVM. However, despite enabling the necessary configs and DT nodes, my
> boot flow seemed to be failing. I then came to know that the condition
> causing this failure was that my generated DTB was of odd number of
> bytes.
> So, while loading the dtb from the Octal SPI NOR Flash to the memory,
> the data.nbytes was odd which made the supports_op
> function return false. This check feels a little too strict at the
> spi-mem stage and we should let the controller decide what to do in case
> of odd bytes in DTR. After applying this patch, I was able to
> succesfully boot the AM62SK EVM without any issues.
> 
> I would also like to justify this patch by pointing the community to the
> equivalent code in the linux kernel, in drivers/spi/spi-mem.c, where this check
> is absent as well.
> 
> The controller does work with odd number of bytes and I have not seen
> any sort of bugs in the absence of this supports_op check. Hence, feel
> that it is safe enough to discard this check from here.
> 
>   drivers/spi/spi-mem.c | 4 ----
>   1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
> index 8e8995fc537f..eecc13bec90d 100644
> --- a/drivers/spi/spi-mem.c
> +++ b/drivers/spi/spi-mem.c
> @@ -181,10 +181,6 @@ bool spi_mem_dtr_supports_op(struct spi_slave *slave,
>   	if (op->dummy.nbytes && op->dummy.buswidth == 8 && op->dummy.nbytes % 2)
>   		return false;
>   
> -	if (op->data.dir != SPI_MEM_NO_DATA &&
> -	    op->dummy.buswidth == 8 && op->data.nbytes % 2)
> -		return false;
> -
>   	return spi_mem_check_buswidth(slave, op);
>   }
>   EXPORT_SYMBOL_GPL(spi_mem_dtr_supports_op);

-- 
Thanks and Regards,
Dhruva Gole