Stephen Boyd <[email protected]> writes: > On 05/28, Stephen Warren wrote: >> On 05/18/2015 01:43 PM, Eric Anholt wrote: >> > Unfortunately, the clock manager's registers are not accessible by the >> > ARM, so we have to request that the firmware modify our clocks for us. >> > >> > This driver only registers the clocks at the point they are requested >> > by a client driver. This is partially to support returning >> > -EPROBE_DEFER when the firmware driver isn't supported yet, but it >> > also avoids issues with disabling "unused" clocks due to them not yet >> > being connected to their consumers in the DT. >> >> It looks like you forgot to CC the clock subsystem maintainers: >> >> M: Mike Turquette <[email protected]> >> M: Stephen Boyd <[email protected]> >> > > Thanks, except I don't have the full patch context here to review > the patch. > >> The description above sounds like a neat solution, but has the >> disadvantage that the clocks without a client won't show up in debugfs. >> I wonder if the clock maintainers know of a better way? > > Can you mark them as CLK_IGNORE_UNUSED? The probe defer problem > has a solution in sight (see more below).
>> > + init.flags = CLK_IS_ROOT;
>>
>> Is it possible to add clock parent information to the driver, so the
>> clocks are all hooked together into the correct tree, rather than all
>> looking like root clocks?
>>
>> One of the many reasons I didn't do anything FW-wise for the kernel was
>> the hope that such information would be forthcoming, and hence we could
>> have complete kernel drivers.
>>
>> > +void __init rpi_firmware_init_clock_provider(struct device_node *node)
>> > +{
>> > + /* We delay construction of our struct clks until get time,
>> > + * because we need to be able to return -EPROBE_DEFER if the
>> > + * firmware driver isn't up yet. clk core doesn't support
>> > + * re-probing on -EPROBE_DEFER, but callers of clk_get can.
>>
>> Oh, that's nasty. What would it take to fix the clock core to support
>> deferred probe? It really should.
>
> There are patches to support probe defer from clk_get() but they
> stalled because sunxi is needs to keep clocks on from their
> providing driver (termed "critical clocks"). If we can resolve
> the "critical clocks" thing then we should be able to support
> probe defer, unless we find other users of orphaned clk
> pointers.
Great! I'm certainly happy to switch to a normal registration of all my
clocks once -EPROBE_DEFER works from the clock provider init.
If those patches aren't landing this release, that also gives us a
release to wire up all the clock consumers in the DT before we get hit
by stable DT ABI, so we'll be able to give a nice limited set of
CLOCK_IGNORE_UNUSED in the flags when we transition.
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