[RFC 02/10] mtd: spi-nor: Use the highest supported READ protocol

[Cyrille Pitchen]

Hi Prabhakar,

Le 06/12/2017 à 09:15, Prabhakar Kushwaha a écrit :
> HWCAP read capabilities defines higher bit position as the higher
> priority. i.e. use Octo SPI protocols first, then Quad SPI protocols
> before Dual SPI protocols, Fast Read and lastly (Slow) Read.
> 
> Currently implementation chose the last set bit i.e. slowest read.
> This patch select the highest available read capability.
> 
> Signed-off-by: Prabhakar Kushwaha <prabhakar.kushwaha at nxp.com>
> ---
>  drivers/mtd/spi-nor/spi-nor.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 7d3b52f..01898e1 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -2521,7 +2521,7 @@ static int spi_nor_select_read(struct spi_nor *nor,
>  			       const struct spi_nor_flash_parameter *params,
>  			       u32 shared_hwcaps)
>  {
> -	int cmd, best_match = fls(shared_hwcaps & SNOR_HWCAPS_READ_MASK) - 1;
> +	int cmd, best_match = ffs(shared_hwcaps & SNOR_HWCAPS_READ_MASK) - 1;

I'm pretty sure this patch is wrong and fls() - find last
(most-significant) bit set - is actually what we want to select the best match.

Is the implementation of fls() correct on your platform ?

Best regards,

Cyrille

>  	const struct spi_nor_read_command *read;
>  
>  	if (best_match < 0)
>