[PATCH v1 1/2] clk: socfpga: Read the clock parent's register base in probe function

[Simon Glass]

Hi,

On Tue, 31 Mar 2020 at 20:33, Ang, Chee Hong <chee.hong.ang at intel.com> wrote:
>
> > Hi Marek,
> >
> > On Wed, 11 Mar 2020 at 05:55, Marek Vasut <marex at denx.de> wrote:
> > >
> > > On 3/11/20 12:50 PM, Simon Glass wrote:
> > > > Hi,
> > >
> > > Hi,
> > >
> > > > On Mon, 9 Mar 2020 at 02:22, <chee.hong.ang at intel.com> wrote:
> > > >>
> > > >> From: Chee Hong Ang <chee.hong.ang at intel.com>
> > > >>
> > > >> This commit (82de42fa14682d408da935adfb0f935354c5008f) calls
> > > >> child's
> > > >> ofdata_to_platdata() method before the parent is probed in dm core.
> > > >> This has caused the driver no longer able to get the correct parent
> > > >> clock's register base in the ofdata_to_platdata() method because
> > > >> the parent clocks will only be probed after the child's ofdata_to_platdata().
> > > >> To resolve this, the clock parent's register base will only be
> > > >> retrieved by the child in probe() method instead of ofdata_to_platdata().
> > > >
> > > > I think one thing that is going on here is that DM allows ofdata to
> > > > be read for a device before its parent devices have been read, but
> > > > it requires that parent devices be probed before their children.
> > >
> > > This seems wrong. The clock driver should be able to instantiate
> > > devices and read their ofdata without probing them. That is one of the
> > > core design principles of the DM.
> >
> > That's a different question. Yes you can read ofdata without probing a device.
> > That's why we have two methods.
> >
> > The point I am making is that at present there is no requirement that a parent's
> > ofdata be read before a child's ofdata is read. But there is a requirement that a
> > parent be probed before a child is probed.
> >
> > >
> > > > The idea is that it should be possible to read the ofdata for a node
> > > > without needing to have done so for parents. But perhaps this
> > > > assumption is too brave?
> > >
> > > Why is it brave ? That's how it always was, the DT is already there,
> > > so why wouldn't you be able to read it.
> >
> > That was my thinking too. But we are finding in a few situations that the child's
> > ofdata depends on the parent's. For example, the parent may have a base
> > address, or a range mapping, or something else that is needed for the child to
> > correctly get its base address, etc.
> >
> > >
> > > > I suspect we could change this, so that device_ofdata_to_platdata()
> > > > first calls itself on its parent.
> > > >
> > > > I can think of various reasons why this change might be desirable.
> > >
> > > I think this is how it worked before already.
> >
> > Well effectively, yes, because ofdata and probe were joined together.

> Simon, do you have plan to fix this DM core issue ?

I'm not sure it definitely should be changed. But I'll do a patch and
see how it looks.

Regards,
Simon