[linux-sunxi] Re: [PATCH v4 0/5] simplefb: add clock handling code

[Rob Herring]

On Wed, Oct 29, 2014 at 7:08 PM, Tomi Valkeinen <tomi.valkeinen at ti.com> wrote:
> Hi Hans, Rob,
>
> On 28/10/14 13:30, Hans de Goede wrote:
>> Hi,
>>
>> On 10/28/2014 12:11 PM, Rob Herring wrote:
>
>>> Yes, I object to the binding still as it has not changed from what was
>>> previously posted.
>>
>> It would be helpful if you could explain why you object. Last time you
>> said: " You are mixing in a hardware description that is simply inaccurate."
>>
>> I then explained that this is not hardware description, but runtime state
>> information, as it tells the kernel which clocks were chosen to drive the
>> display (out of typically a list of possible options, depending on which
>> output is used, etc.). Just like which memory address the bootloader has
>> chosen to scan out the video image from.
>>
>> Then you got quiet, so sorry, but this time your objection really is too
>> late. You cannot simply go quiet halfway through a discussion and then pop
>> up again when a new version is posted to say "I object" yet another time,
>> you've had your chance to make your arguments last time, and chose to stay
>> quiet after I explained in detail that this is not hardware description but
>> state information, so now it is simply too late.
>>
>> These bindings have been discussed at Plumbers with various interested people
>> present, and the conclusion was that this really is the best way to handle this,
>> so this patch is:
>>
>>     Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>>     Reviewed-by: Mike Turquette <mturquette at linaro.org>
>>     Acked-by: Geert Uytterhoeven <geert at linux-m68k.org>
>>     Reviewed-by: Maxime Ripard <maxime.ripard at free-electrons.com>
>>
>> And David Herrman who is working on simpledrm, which will be merged soon, which
>> will also use the simplefb bindings also agrees. So we have the simplefb maintainer,
>> simpledrm maintainer, and the clk subsystem maintainer + 2 other maintainers all
>> agreeing on a way forward, the time for bikeshedding now really really really is
>> over.
>>
>> Tomi, can you please let us know how you plan to proceed with this ?
>
> I won't merge DT bindings via fbdev tree, if a DT maintainer says no.
>
> I took Rob's silence to the earlier series as a silent ack for your
> explanation. Obviously that was not the case.
>
> Rob, please advice asap what should be done to the bindings to get your
> ack. As Hans explained above, this discussion has been going on for a
> long time, and afaik this series is the best way forward of all the
> options discussed.

I still think for the most part this is a kernel problem. It is a
kernel policy to turn off unused clocks. The clock framework could
just as easily decide that any clocks enabled at boot and left
un-managed (i.e. w/o a driver) are kept on until they are managed. I'm
not saying this can't be in DT, only that DT is not the only solution
here. This problem is not unique to simplefb. A serial console could
stop working if no serial driver is loaded before unused clocks are
disabled. CPU core clocks have a similar issue as well (often enabled
in platform code). I want to see this solved in a generic way for any
clock.

As regulators were also mentioned, they already have a
"regulator-boot-on" property defined. Perhaps this is suitable to be
mirrored for clocks. If it is not, then I'm wondering why we have it.
A key difference here is that the property is part of the provider and
can be dealt with in the clock driver rather than requiring a
temporary driver.

Rob