Re: [PATCH v5 12/44] clk: davinci: Add platform information for TI DA850 PSC

[David Lechner]

On 04/05/2018 09:36 AM, Sekhar Nori wrote:
> On Thursday 05 April 2018 07:14 PM, Bartosz Golaszewski wrote:
> > 2018-04-05 15:09 GMT+02:00 Sekhar Nori <nsekhar@xxxxxx>:
> > > Hi Bartosz,
> > >
> > > On Friday 09 February 2018 10:18 PM, Michael Turquette wrote:
> > > > On Fri, Feb 9, 2018 at 8:22 AM, Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> > > > > 2018-01-08 3:17 GMT+01:00 David Lechner <david@xxxxxxxxxxxxxx>:
> > >
> > > > > Hi David,
> > > > >
> > > > > I've been working on moving the genpd code from its own driver to the
> > > > > psc one. I couldn't get the system to boot though and problems
> > > > > happened very early in the boot sequence. I struggled to figure out
> > > > > what's happening, but eventually I noticed that psc uses
> > > > > CLK_OF_DECLARE() to initialize clocks. The functions registered this
> > > > > way are called very early in the boot sequence, way before
> > > > > late_initcall() in which the genpd framework is initialized. This of
> > >
> > > late_initcall() is too late for genpd to be initialized. As you may have
> > > seen with the latest set of patches, we have problems with timer
> > > initialization. After converting to platform devices, PSC and PLL clocks
> > > get initialized post time_init(). We are working that around using
> > > fixed-clocks, which hopefully will work (I still need to test many of
> > > the affected platforms).
> > >
> > > Can you please reply with the exact issue you faced with genpd framework
> > > initialization so we do have that on record.
> >
> > The exact issue manifested itself in a NULL-pointer dereference panic
> > when I tried moving the genpd code I had initially implemented as a
> > separate platform driver to what I believe was v6 or v7 of David's
> > series (before the psc driver became a platform driver, when it was
> > still using CLK_OF_DECLARE()). When I had tested a simple conversion
> > of that version to a platform_driver, genpd worked fine.
> >
> > I don't have the stack traces from these panics, but I recall some
> > debugfs functions being involved and the genpd late_initcalls are
> > related to debugfs. Looking at it now I don't see how exactly it could
> > fail though.
>
> Do you have the code where you faced the problem stashed somewhere? I am
> not (yet) advocating going back to CLK_OF_DECLARE(). But there is a
> definite issue with timer being ready when not using CLK_OF_DECLARE().
> So, I want to make sure there the reason why we are going down the
> platform device path is a amply clear.
>
> Thanks,
> Sekhar
This is the thread that led to the conversion to platform devices:

https://lkml.org/lkml/2018/2/9/541