Re: [PATCH v5 12/44] clk: davinci: Add platform information for TI DA850 PSC

[Bartosz Golaszewski]

2018-04-05 16:36 GMT+02:00 Sekhar Nori <nsekhar@xxxxxx>:
> On Thursday 05 April 2018 07:14 PM, Bartosz Golaszewski wrote:
>> 2018-04-05 15:09 GMT+02:00 Sekhar Nori <nsekhar@xxxxxx>:
>>> Hi Bartosz,
>>>
>>> On Friday 09 February 2018 10:18 PM, Michael Turquette wrote:
>>>> On Fri, Feb 9, 2018 at 8:22 AM, Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
>>>>> 2018-01-08 3:17 GMT+01:00 David Lechner <david@xxxxxxxxxxxxxx>:
>>>
>>>>> Hi David,
>>>>>
>>>>> I've been working on moving the genpd code from its own driver to the
>>>>> psc one. I couldn't get the system to boot though and problems
>>>>> happened very early in the boot sequence. I struggled to figure out
>>>>> what's happening, but eventually I noticed that psc uses
>>>>> CLK_OF_DECLARE() to initialize clocks. The functions registered this
>>>>> way are called very early in the boot sequence, way before
>>>>> late_initcall() in which the genpd framework is initialized. This of
>>>
>>> late_initcall() is too late for genpd to be initialized. As you may have
>>> seen with the latest set of patches, we have problems with timer
>>> initialization. After converting to platform devices, PSC and PLL clocks
>>> get initialized post time_init(). We are working that around using
>>> fixed-clocks, which hopefully will work (I still need to test many of
>>> the affected platforms).
>>>
>>> Can you please reply with the exact issue you faced with genpd framework
>>> initialization so we do have that on record.
>>>
>>
>> The exact issue manifested itself in a NULL-pointer dereference panic
>> when I tried moving the genpd code I had initially implemented as a
>> separate platform driver to what I believe was v6 or v7 of David's
>> series (before the psc driver became a platform driver, when it was
>> still using CLK_OF_DECLARE()). When I had tested a simple conversion
>> of that version to a platform_driver, genpd worked fine.
>>
>> I don't have the stack traces from these panics, but I recall some
>> debugfs functions being involved and the genpd late_initcalls are
>> related to debugfs. Looking at it now I don't see how exactly it could
>> fail though.
>
> Do you have the code where you faced the problem stashed somewhere? I am
> not (yet) advocating going back to CLK_OF_DECLARE(). But there is a
> definite issue with timer being ready when not using CLK_OF_DECLARE().
> So, I want to make sure there the reason why we are going down the
> platform device path is a amply clear.
>
> Thanks,
> Sekhar

Yes, you can still find it on my github[1].

Bart

[1] github.com:brgl/linux.git  topic/davinci-genpd-final-v2