RE: [PATCH v3 1/5] dt-bindings: spi: Add SSTE support for DWC SSI controller

[Srikandan, Nandhini]

> -----Original Message-----
> From: Serge Semin <fancer.lancer@xxxxxxxxx>
> Sent: Thursday, November 11, 2021 8:37 PM
> To: Mark Brown <broonie@xxxxxxxxxx>; Srikandan, Nandhini
> <nandhini.srikandan@xxxxxxxxx>
> Cc: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>; robh+dt@xxxxxxxxxx;
> linux-spi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; mgross@xxxxxxxxxxxxxxx; Pan, Kris
> <kris.pan@xxxxxxxxx>; Demakkanavar, Kenchappa
> <kenchappa.demakkanavar@xxxxxxxxx>; Zhou, Furong
> <furong.zhou@xxxxxxxxx>; Sangannavar, Mallikarjunappa
> <mallikarjunappa.sangannavar@xxxxxxxxx>; Vaidya, Mahesh R
> <mahesh.r.vaidya@xxxxxxxxx>; A, Rashmi <rashmi.a@xxxxxxxxx>
> Subject: Re: [PATCH v3 1/5] dt-bindings: spi: Add SSTE support for DWC SSI
> controller
> 
> On Thu, Nov 11, 2021 at 03:01:12PM +0000, Mark Brown wrote:
> > On Thu, Nov 11, 2021 at 05:31:08PM +0300, Serge Semin wrote:
> >
> > > BTW Mark, why not to have a generic DT-property which would set that
> > > flag automatically by the SPI-core subsystem seeing it's indeed a
> > > client device-property? For instance there can be some property like
> > > "spi-cs-toggle" DT-property which when specified for the particular
> > > SPI-client DT-node will make the SPI-core subsystem to set the
> >
> > Anything like this is fundamentally part of the wire protocol for the
> > device, there's no need for an extra property on top of the compatible
> > for the device and the driver really, really needs to know what's
> > going on to avoid data corruption.  You could also use this feature
> > together with varying the word size as an optimisation at runtime (eg,
> > do long sequences of register writes in a single hardware operation by
> > setting an appropriate word length to cause the controller to bounce
> > chip select between writes).
> >
> > > SPI_CS_WORD flag of the device mode? Like it has already been done
> > > for "spi-cs-high"/"spi-lsb-first"/etc.
> >
> > I don't think either of those properties was a good idea, there's a
> > bunch of stuff in the older SPI bindings that don't make much sense.
> 
> Ok. Thanks for clarification. No new DT-property then.
> 
> Nandhini, could you please drop this patch in v4? One more time I'm sorry
> for misleading you on v2.

Sure, I will make use of SPI_CS_WORD flag and drop this patch in next version. 

> 
> -Sergey