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

[Simon Glass]

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.

Regards,
Simon