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

[Kuldeep Singh <kuldeep.singh@xxxxxxx>]

> -----Original Message-----
> From: Bough Chen <haibo.chen@xxxxxxx>
> Sent: Wednesday, September 1, 2021 1:35 PM
> To: Kuldeep Singh <kuldeep.singh@xxxxxxx>
> Cc: linux-spi@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; Rajesh
> Bhagat <rajesh.bhagat@xxxxxxx>; broonie@xxxxxxxxxx
> Subject: RE: [EXT] [PATCH 3/4] spi: spi-nxp-fspi: add DDR mode support
> 
> > -----Original Message-----
> > From: Kuldeep Singh
> > Sent: 2021年8月31日 18:42
> > To: Bough Chen <haibo.chen@xxxxxxx>
> > Cc: linux-spi@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; Bough
> Chen
> > <haibo.chen@xxxxxxx>; Rajesh Bhagat <rajesh.bhagat@xxxxxxx>;
> > broonie@xxxxxxxxxx
> > Subject: RE: [EXT] [PATCH 3/4] spi: spi-nxp-fspi: add DDR mode support
> >
> > 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.
> 
> Thanks for your comments!
> The flexspi controller in Layerscape support 8bit DTR, but for flexspi, if
> support 8bit DTR, need to use mode3, which means we must connect the DQS
> pad
> on board.
> Seems LX216x board do not connect DQS line.
> We should take this into consideration, this is board limitation, better to
> involve a property in device-tree.
> I will send a V2 patch soon.

Thanks for your understanding.
I will make sure to confirm NXP layerscape devices for next version of series.

Regards
Kuldeep