Re: [PATCH v4 5/5] clk: qcom: Add Global Clock controller (GCC) driver for SC7180

[Stephen Boyd <sboyd@kernel.org>]

Quoting Rob Clark (2019-11-08 11:40:53)
> On Fri, Nov 8, 2019 at 10:42 AM Stephen Boyd <sboyd@kernel.org> wrote:
> >
> > So the scenario is DT describes the clk
> >
> >  dpu_node {
> >      clocks = <&cc AHB_CLK>;
> >      clock-names = "iface";
> >  }
> >
> > but the &cc node has a driver that doesn't probe?
> >
> > I believe in this scenario we return -EPROBE_DEFER because we assume we
> > should wait for the clk driver to probe and provide the iface clk. See
> > of_clk_get_hw_from_clkspec() and how it looks through a list of clk
> > providers and tries to match the &cc phandle to some provider.
> >
> > Once the driver probes, the match will happen and we'll be able to look
> > up the clk in the provider with __of_clk_get_hw_from_provider(). If
> > the clk provider decides that there isn't a clk object, it will return
> > NULL and then eventually clk_hw_create_clk() will turn the NULL return
> > value into a NULL pointer to return from clk_get().
> >
> 
> ok, that was the scenario I was worried about (since unclk'd register
> access tends to be insta-reboot and hard to debug)..  so I think it
> should be ok to make dpu just ignore NULL clks.
> 
> From a quick look, I think something like the attached (untested).
> (Sorry, I'd just paste it inline but gmail somehow eats all the
> whitespace when I do that :-/)

Cool. Looks good to me.