[linux-sunxi] Re: [PATCH v3] dt-bindings: Add a clocks property to the simple-framebuffer binding

[Geert Uytterhoeven]

On Fri, Oct 3, 2014 at 10:55 PM, jonsmirl at gmail.com <jonsmirl at gmail.com> wrote:
> On Thu, Oct 2, 2014 at 9:46 AM, Geert Uytterhoeven <geert at linux-m68k.org> wrote:
>> On Thu, Oct 2, 2014 at 3:34 PM, jonsmirl at gmail.com <jonsmirl at gmail.com> wrote:
>>> Does the clock and regulator cleanup happen before drivers can load
>>> off from initrd? I didn't think it did but I might be wrong.
>>
>> Yes
>>
>> drivers/base/power/domain.c:late_initcall(genpd_poweroff_unused);
>> drivers/clk/clk.c:late_initcall_sync(clk_disable_unused);
>> drivers/regulator/core.c:late_initcall_sync(regulator_init_complete);
>
> What do you think about putting these calls onto an ioctl somewhere
> and then eliminating the late_initcall(..)? A tiny user space app
> could then hit that ioctl after all of the loadable device drivers are
> loaded. Add the command to make this ioctl call to busybox or udev.
> After all, it is not fatal if these calls aren't made, all they do is
> save power. Add a link in rc.d or somewhere similar to run this app at
> the appropriate time.
>
> Switching these over to an ioctl allows a window to be opened for
> device specific driver loading before the clock/regulator clean up
> happens.
>
> Now all of this mess of protecting clocks and regulator disappears.
> Instead get the device specific drivers written and loaded, then run
> the cleanup app which hits the ioctl(). All of the correct
> clock/regulators will be claimed and then this clean code will do the
> right thing.
>
> From my perspective it appears that this cleanup is being done too
> early which then triggers a need to protect things from cleanup.

Not doing the cleanup doesn't help.

If someone else calls clk_disable() on a clock which shares a parent
with the clock you're silently using, that clock will still be disabled.
This can happen at any time.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds