Re: [PATCH -next 1/2] i2c: designware: Switch from using MMIO access to SMN access

Andy Shevchenko
2022-09-22T09:51:26Z

+Cc: Hans (mentioned your name and was under impression that you are in Cc list already)

On Thu, Sep 22, 2022 at 12:49:15PM +0300, Andy Shevchenko wrote:
> On Wed, Sep 21, 2022 at 10:50:53PM +0200, Borislav Petkov wrote:
> > On Wed, Sep 21, 2022 at 03:19:26PM -0500, Limonciello, Mario wrote:
> > > Jan mentioned this in the commit message:
> > >
> > > > The function which registers i2c-designware-platdrv is a
> > > > subsys_initcall that is executed before fs_initcall (when enumeration > of
> > > NB descriptors occurs).
> > >
> > > So if it's not exported again, then it means that we somehow
> > > need to get i2c-designware-platdrv to register earlier too.
> >
> > So I have this there:
> >
> > /* This has to go after the PCI subsystem */
> > fs_initcall(init_amd_nbs);
> >
> > as I need PCI. It itself does
> >
> > arch_initcall(pci_arch_init);
> >
> > so I guess init_amd_nbs() could be a subsys_initcall...
> >
> > Or why is
> >
> > subsys_initcall(dw_i2c_init_driver);
> >
> > a subsys initcall in the first place?
> >
> > Looking at
> >
> > 104522806a7d ("i2c: designware: dw_i2c_init_driver as subsys initcall")
> >
> > I don't see a particular reason why it should be a subsys_initcall...
> >
> > In any case, this should be fixed without an export which was crap in
> > the first place.
> >
> > Hm.
>
> I'm speculating here, but IIRC the I2C controllers may serve PMICs on some
> platform that are required to be present earlier due to some ACPI code
> accessing them. This Hans de Goede can confirm or correct me.
>
> Another case comes to my mind is that I2C framework wants to initialize I2C
> peripherals which were supplied via struct i2c_board_info on earlier stages.
> And again comes to the specifics of the certain peripherals that needs for
> power / reset / etc control, i.o.w. critical hardware for the platforms.
>
> But it's still what I remember and I can be mistaken.

--
With Best Regards,
Andy Shevchenko