linux-kernel - Re: [PATCH v2 3/3] clk: meson: a1: add support for Amlogic A1 clock driver

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Date:   Mon, 25 Nov 2019 20:01:56 +0800
From:   Jian Hu <jian.hu@...ogic.com>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>
CC:     Kevin Hilman <khilman@...libre.com>, Rob Herring <robh@...nel.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Qiufang Dai <qiufang.dai@...ogic.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        Chandle Zou <chandle.zou@...ogic.com>,
        <linux-clk@...r.kernel.org>, <linux-amlogic@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] clk: meson: a1: add support for Amlogic A1 clock
 driver



On 2019/11/25 18:14, Jerome Brunet wrote:
> 
> On Thu 21 Nov 2019 at 04:21, Jian Hu <jian.hu@...ogic.com> wrote:
> 
>> Hi, Jerome
>>
>> On 2019/11/20 23:35, Jerome Brunet wrote:
>>>
>>> On Wed 20 Nov 2019 at 10:28, Jian Hu <jian.hu@...ogic.com> wrote:
>>>
>>>> Hi, jerome
>>>>
>>>> Is there any problem about fixed_pll_dco's parent_data?
>>>>
>>>> Now both name and fw_name are described in parent_data.
>>>
>>> Yes, there is a problem.  This approach is incorrect, as I've tried to
>>> explain a couple times already. Let me try to re-summarize why this
>>> approach is incorrect.
>>>
>>> Both fw_name and name should be provided when it is possible that
>>> the DT does not describe the input clock. IOW, it is only for controllers
>>> which relied on the global name so far and are now starting to describe
>>> the clock input in DT
>>>
>>> This is not your case.
>>> Your controller is new and DT will have the correct
>>> info
>>>
>>> You are trying work around an ordering issue by providing both fw_name
>>> and name. This is not correct and I'll continue to nack it.
>>>
>>> If the orphan clock is not reparented as you would expect, I suggest you
>>> try to look a bit further at how the reparenting of orphans is done in
>>> CCF and why it does not match your expectation.
>>>
>> I have debugged the handle for orphan clock in CCF, Maybe you are missing
>> the last email.
> 
> Nope, got it the first time
> 
>> Even though the clock index exit, it will get failed for the orphan clock's
>> parent clock due to it has not beed added to the provider.
> 
> If the provider is not registered yet, of course any query to it won't
> work. This why I have suggested to this debug *further* :
> 
> * Is the orphan reparenting done when a new provider is registered ?
> * If not, should it be done ? is this your problem ?
> 
Yes, the orphan reparenting is done when the new provider is registered.

Reparenting the orphan will be done when each clock is registered by 
devm_clk_hw_register. And at this time the provider has not been 
registered. After all clocks are registered by devm_clk_hw_register, the
provider will be registered by devm_of_clk_add_hw_provider.

Reparenting the orphan will fail when fw_name is added alone, the couse 
is that devm_clk_hw_register is always running ahead of 
devm_of_clk_add_hw_provider.

That is why it will failed to get parent for the orphan clock.



> 
> .
>