RE: [PATCH v3 3/5] spi: dw: Add support for master mode selection for DWC SSI controller

["Srikandan, Nandhini" <nandhini.srikandan@intel.com>]

> -----Original Message-----
> From: Srikandan, Nandhini
> Sent: Wednesday, November 17, 2021 5:29 PM
> To: Serge Semin <fancer.lancer@gmail.com>; Mark Brown
> <broonie@kernel.org>
> Cc: Serge Semin <Sergey.Semin@baikalelectronics.ru>; robh+dt@kernel.org;
> linux-spi@vger.kernel.org; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org; mgross@linux.intel.com; Pan, Kris
> <kris.pan@intel.com>; Demakkanavar, Kenchappa
> <kenchappa.demakkanavar@intel.com>; Zhou, Furong
> <furong.zhou@intel.com>; Sangannavar, Mallikarjunappa
> <mallikarjunappa.sangannavar@intel.com>; Vaidya, Mahesh R
> <mahesh.r.vaidya@intel.com>; A, Rashmi <Rashmi.A@intel.com>
> Subject: RE: [PATCH v3 3/5] spi: dw: Add support for master mode selection
> for DWC SSI controller
> 
> 
> 
> > -----Original Message-----
> > From: Serge Semin <fancer.lancer@gmail.com>
> > Sent: Wednesday, November 17, 2021 12:46 AM
> > To: Mark Brown <broonie@kernel.org>; Srikandan, Nandhini
> > <nandhini.srikandan@intel.com>
> > Cc: Serge Semin <Sergey.Semin@baikalelectronics.ru>;
> > robh+dt@kernel.org; linux-spi@vger.kernel.org;
> > linux-kernel@vger.kernel.org; devicetree@vger.kernel.org;
> > mgross@linux.intel.com; Pan, Kris <kris.pan@intel.com>; Demakkanavar,
> > Kenchappa <kenchappa.demakkanavar@intel.com>; Zhou, Furong
> > <furong.zhou@intel.com>; Sangannavar, Mallikarjunappa
> > <mallikarjunappa.sangannavar@intel.com>; Vaidya, Mahesh R
> > <mahesh.r.vaidya@intel.com>; A, Rashmi <rashmi.a@intel.com>
> > Subject: Re: [PATCH v3 3/5] spi: dw: Add support for master mode
> > selection for DWC SSI controller
> >
> > On Thu, Nov 11, 2021 at 04:25:02PM +0000, Mark Brown wrote:
> > > On Thu, Nov 11, 2021 at 07:06:27PM +0300, Serge Semin wrote:
> > > > On Thu, Nov 11, 2021 at 03:14:26PM +0000, Mark Brown wrote:
> > >
> > > > > Given that people seem to frequently customise these IPs when
> > > > > integrating them I wouldn't trust people not to have added some
> > > > > other control into that reserved bit doing some magic stuff
> > > > > that's useful in their system.
> > >
> > > > In that case the corresponding platform code would have needed to
> > > > have that peculiarity properly handled and not to use a generic
> > > > compatibles like "snps,dwc-ssi-1.01a" or "snps,dw-apb-ssi", which
> > > > are supposed to be utilized for the default IP-core configs only.
> > > > For the sake of the code simplification I'd stick to setting that
> > > > flag for each generic DWC SSI-compatible device. That will be also
> > > > helpful for DWC SSIs which for some reason have the slave-mode
> > enabled by default.
> > >
> >
> > > That's easier right up until the point where it explodes - I'd
> > > prefer to be more conservative here.  Fixing things up after the
> > > fact gets painful when people end up only finding the bug in
> > > released kernels, especially if it's distro end users or similar rather than
> developers.
> >
> > Since IP-core and components versions is now supported that will easy
> > to implement. Thanks for merging the corresponding series in BTW.
> >
> > >
> > > > Alternatively the driver could read the IP-core version from the
> > > > DW_SPI_VERSION register, parse it (since it's in ASCII) and then
> > > > use it in the conditional Master mode activation here. But that
> > > > could have been a better solution in case if the older IP-cores
> > > > would have used that bit for something special, while Nandhini
> > > > claims it was
> > reserved.
> > > > So in this case I would stick with a simpler approach until we get
> > > > to face any problem in this matter, especially seeing we already
> > > > pocking the reserved bits of the CTRL0 register in this driver in
> > > > the
> > > > spi_hw_init() method when it comes to the DFS field width detection.
> > >
> > > If the device has a version register checking that seems ideal - the
> > > infrastructure will most likely be useful in future anyway.  A bit
> > > of a shame that it's an ASCII string though.
> >
> > That's what the patchset has been implemented for in the first place
> > https://lore.kernel.org/linux-spi/20211115181917.7521-1-
> > Sergey.Semin@baikalelectronics.ru/
> >
> > Nandhini, Mark has just merged in the series that adds the IP-core
> > versions infrastructure support to the DW SSI driver.  So now you can
> > easily convert this patch to be using that new interface like this:
> > -               if (dws->caps & DW_SPI_CAP_KEEMBAY_MST)
> > -                       cr0 |= DWC_SSI_CTRLR0_KEEMBAY_MST;
> > +               /* CTRLR0[31] MST */
> > +		if (dw_spi_ver_is_ge(dws, HSSI, 102A))
> > +       	        cr0 |= DWC_HSSI_CTRLR0_MST;
> >
> > Please don't forget to convert the DWC_SSI_CTRLR0_KEEMBAY_MST name
> to
> > something like DWC_HSSI_CTRLR0_MST and place it at the top of the DWC
> > HSSI CTRLR0 register macros list.
> >
> > -Sergey
> Sure, I will test this patch set on our hardware and then use the IP-core
> version infrastructure support and make the changes as mentioned for MST
> bit.
> 
> - Nandhini
I have tested the patches on our hardware and it is working fine. When would these patches be available in mainline? So that I can start applying the changes on top of these patches and share for review.
- Nandhini