> -----Original Message----- > From: Serge Semin <fancer.lancer@xxxxxxxxx> > Sent: Wednesday, November 17, 2021 12:46 AM > 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 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@xxxxxxxxxxxxxxxxxxxx/ > > 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
