[PATCH v3 0/2] clk: improve handling of orphan clocks

[Sascha Hauer]

On Thu, May 07, 2015 at 11:53:18PM -0700, Stephen Boyd wrote:
> On 05/07, Kevin Hilman wrote:
> > On Thu, May 7, 2015 at 2:03 PM, Stephen Boyd <sboyd at codeaurora.org> wrote:
> > > On 05/07/15 08:17, Kevin Hilman wrote:
> > >> On Fri, May 1, 2015 at 4:40 PM, Stephen Boyd <sboyd at codeaurora.org> wrote:
> > >>> On 05/01/15 15:07, Heiko Stübner wrote:
> > >>>> Am Freitag, 1. Mai 2015, 13:52:47 schrieb Stephen Boyd:
> > >>>>
> > >>>>>> Instead I guess we could hook it less deep into clk_get_sys, like in the
> > >>>>>> following patch?
> > >>>>> It looks like it will work at least, but still I'd prefer to keep the
> > >>>>> orphan check contained to clk.c. How about this compile tested only patch?
> > >>>> I gave this a spin on my rk3288-firefly board. It still boots, the clock tree
> > >>>> looks the same and it also still defers nicely in the scenario I needed it
> > >>>> for. The implementation also looks nice - and of course much more compact than
> > >>>> my check in two places :-) . I don't know if you want to put this as follow-up
> > >>>> on top or fold it into the original orphan-check, so in any case
> > >>>>
> > >>>> Tested-by: Heiko Stuebner <heiko at sntech.de>
> > >>>> Reviewed-by: Heiko Stuebner <heiko at sntech.de>
> > >>> Thanks. I'm leaning towards tossing your patch 2/2 and replacing it with
> > >>> my patch and a note that it's based on an earlier patch from you.
> > >> It appears this has landed in linux-next in the form of 882667c1fcf1
> > >> clk: prevent orphan clocks from being used.  A bunch of boot failures
> > >> for sunxi in today's linux-next[1] were bisected down to that patch.
> > >>
> > >> I confirmed that reverting that commit on top of next/master gets
> > >> sunxi booting again.
> > >>
> > >>
> > >
> > > Thanks for the report. I've removed the two clk orphan patches from
> > > clk-next. Would it be possible to try with next-20150507 and
> > > clk_ignore_unused on the command line?
> > 
> > That doesn't help.  I tried on cubieboard2 and bananapi.
> 
> Thanks for trying.
> 
> > 
> > > Also we can try to see if
> > > critical clocks aren't being forced on by applying this patch and
> > > looking for clk_get() failures
> > 
> > From cubieboard2, there's a few that look rather important:
> > 
> > [    0.000000] Additional per-CPU info printed with stalls.
> > [    0.000000] Build-time adjustment of leaf fanout to 32.
> > [    0.000000] RCU restricting CPUs from NR_CPUS=16 to nr_cpu_ids=2.
> > [    0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=32, nr_cpu_ids=2
> > [    0.000000] NR_IRQS:16 nr_irqs:16 16
> > [    0.000000] clk: couldn't get parent clock 0 for /clocks/ahb at 01c20054
> > [    0.000000] Failed to enable critical clock cpu
> > [    0.000000] Failed to enable critical clock pll5_ddr
> > [    0.000000] Failed to enable critical clock ahb_sdram
> > [    0.000000] Architected cp15 timer(s) running at 24.00MHz (virt).
> 
> Ok. So it seems we need to come up with some solution to the
> "critical clocks" problem that doesn't require the individual
> clock drivers to call clk_prepare_enable().

I'm getting more and more unsure if we can really handle the complexity
we get by allowing to register orphaned clocks. On one hand we can't
handle the orphaned clocks properly when we do a clk_prepare/enable on
them, on the other hand we run into trouble when we forbid to
prepare/enable them. The fact that clocks can become orphans by
reparenting them makes it even more complicated.
Maybe allowing orphans is something that has to be revisited.

Sascha

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