RE: [EXT] [PATCH 3/4] spi: spi-nxp-fspi: add DDR mode support

[Kuldeep Singh <kuldeep.singh@xxxxxxx>]

Hi Haibo,

> -----Original Message-----
> From: haibo.chen@xxxxxxx <haibo.chen@xxxxxxx>
> Sent: Friday, August 20, 2021 1:14 PM
> To: Ashish Kumar <ashish.kumar@xxxxxxx>; yogeshgaur.83@xxxxxxxxx;
> broonie@xxxxxxxxxx
> Cc: linux-spi@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; Bough Chen
> <haibo.chen@xxxxxxx>
> Subject: [EXT] [PATCH 3/4] spi: spi-nxp-fspi: add DDR mode support
> 
> Caution: EXT Email
> 
> From: Haibo Chen <haibo.chen@xxxxxxx>
> 
> For LUT, add DDR command support.
> Also use new API spi_mem_dtr_supports_op() to check the DTR mode.
> 
> Signed-off-by: Haibo Chen <haibo.chen@xxxxxxx>

Thanks for submitting patch to support octal DTR.

> ---
>  drivers/spi/spi-nxp-fspi.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/spi/spi-nxp-fspi.c b/drivers/spi/spi-nxp-fspi.c index
> a764eb475aed..f7acad2cbe64 100644
> --- a/drivers/spi/spi-nxp-fspi.c
> +++ b/drivers/spi/spi-nxp-fspi.c
> @@ -486,6 +486,9 @@ static bool nxp_fspi_supports_op(struct spi_mem
> *mem,
>             op->data.nbytes > f->devtype_data->txfifo)
>                 return false;
> 
> +       if (op->cmd.dtr && op->addr.dtr && op->dummy.dtr && op->data.dtr)
> +               return spi_mem_dtr_supports_op(mem, op);
> +
[snip]

Now that spi-nor framework and flexspi driver supports octal DTR, if device-tree specifies RX and TX bus-width as <8,8> ,
then above change will always make sure to select DTR mode and SDR will never get selected.
Please note, Layerscape LX2160A and LX2162A are two platforms which have micron mt35xu512aba (support octal dtr) 
and are causing probe failure with these patches as required dependencies for enabling DTR are not met.

Since framework selects maximum supported capability, I think there should be a mechanism to choose SDR or DTR mode in driver itself.
This will also help for a platform to fallback from DTR to SDR in case DTR doesn't work.
We can enable this feature as a quirk or by reading a property from device-tree.
Please let me know your views.

Regards
Kuldeep