linux-kernel - Re: [PATCH] clk: mediatek: mt8186: Change I2C 4/5/6 ap clocks parent to infra

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Date:   Thu, 26 Oct 2023 10:24:45 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Yu-chang Lee (李禹璋) 
        <Yu-chang.Lee@...iatek.com>,
        "wenst@...omium.org" <wenst@...omium.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Chun-Jie Chen (陳浚桀) 
        <Chun-Jie.Chen@...iatek.com>,
        Miles Chen (陳民樺) 
        <Miles.Chen@...iatek.com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH] clk: mediatek: mt8186: Change I2C 4/5/6 ap clocks parent
 to infra

Il 26/10/23 05:49, Yu-chang Lee (李禹璋) ha scritto:
> On Wed, 2023-10-25 at 13:29 +0200, AngeloGioacchino Del Regno wrote:
>> Il 25/10/23 11:50, Yu-chang Lee (李禹璋) ha scritto:
>>> On Tue, 2023-10-24 at 17:20 +0800, Chen-Yu Tsai wrote:
>>>>    	
>>>> External email : Please do not click links or open attachments
>>>> until
>>>> you have verified the sender or the content.
>>>>    On Tue, Oct 24, 2023 at 3:47 PM Yu-chang Lee (李禹璋)
>>>> <Yu-chang.Lee@...iatek.com> wrote:
>>>>>
>>>>> On Tue, 2023-10-24 at 10:58 +0800, Chen-Yu Tsai wrote:
>>>>>> On Tue, Oct 24, 2023 at 10:52 AM Stephen Boyd <
>>>>>> sboyd@...nel.org>
>>>>>> wrote:
>>>>>>>
>>>>>>> Quoting Chen-Yu Tsai (2023-10-19 22:06:35)
>>>>>>>> On Thu, Oct 19, 2023 at 8:49 PM AngeloGioacchino Del
>>>>>>>> Regno
>>>>>>>> <angelogioacchino.delregno@...labora.com> wrote:
>>>>>>>>>
>>>>>>>>> Fix the parenting of clocks
>>>>>>>>> imp_iic_wrap_ap_clock_i2c{4-6},
>>>>
>>>> as
>>>>>>>>> those
>>>>>>>>> are effectively parented to infra_ao_i2c{4-6} and not
>>>>>>>>> to
>>>>
>>>> the
>>>>>>>>> I2C_AP.
>>>>>>>>> This permits the correct (and full) enablement and
>>>>
>>>> disablement
>>>>>>>>> of the
>>>>>>>>> I2C4, I2C5 and I2C6 bus clocks, satisfying the whole
>>>>>>>>> clock
>>>>
>>>> tree
>>>>>>>>> of
>>>>>>>>> those.
>>>>>>>>>
>>>>>>>>> As an example, when requesting to enable
>>>>>>>>> imp_iic_wrap_ap_clock_i2c4:
>>>>>>>>>
>>>>>>>>> Before: infra_ao_i2c_ap -> imp_iic_wrap_ap_clock_i2c4
>>>>>>>>> After:  infra_ao_i2c_ap -> infra_ao_i2c4 ->
>>>>>>>>> imp_iic_wrap_ap_clock_i2c4
>>>>>>>>>
>>>>>>>>> Fixes: 66cd0b4b0ce5 ("clk: mediatek: Add MT8186 imp i2c
>>>>
>>>> wrapper
>>>>>>>>> clock support")
>>>>>>>>> Signed-off-by: AngeloGioacchino Del Regno <
>>>>>>>>> angelogioacchino.delregno@...labora.com>
>>>>>>>>
>>>>>>>> I'm curious about what led to discovering this error?
>>>>>>>>
>>>>>>>
>>>>>>> Is that an acked-by?
>>>>>>
>>>>>> MediaTek engineers are saying the original code already
>>>>>> matches
>>>>
>>>> the
>>>>>> documentation provided by their hardware engineers. I'm
>>>>>> trying to
>>>>
>>>> get
>>>>>> them to respond on the mailing list.
>>>>>>
>>>>>> ChenYu
>>>>>>
>>>>>
>>>>> After checking with I2C clock hardware designer there is no
>>>>> infra_ao_i2c{4-6} clock gate in between. And the clock document
>>>>> at
>>>>
>>>> hand
>>>>> aslo shows the same result. Generallly speaking, we would like
>>>>> to
>>>>
>>>> keep
>>>>> sw setting align with the hardware design document. I would
>>>>
>>>> recommand
>>>>> not to change this part of code, but enable infra_ao_i2c{4-6}
>>>>> prior
>>>>
>>>> to
>>>>> the usage of imp_iic_wrap_ap_clock_i2c clock.
>>>>
>>>> Are infra_ao_i2c{4-6} actually used by the hardware? If so, for
>>>> what
>>>> purpose?
>>>
>>> According to hardware designer it servers no purpose. Just a legacy
>>> of
>>> previous design...
>>>
>>>> If it is actually needed by the hardware and it is not in the
>>>> existing path,
>>>> then it needs to be described in the device tree and handled by
>>>> the
>>>> driver.
>>>>
>>>> ChenYu
>>>
>>> After reviewing hardware design diagram, hardware designer
>>> concludes
>>> that the clock tree is indeed
>>>
>>> top_i2c -> infra_ao_i2c{4-6}
>>> top_i2c -> infra_ao_i2c_ap -> imp_iic_wrap_ap_clock_i2c{4-6}
>>>
>>> so I think we should keep this clock relation unchanged.
>>>
>>> Thanks
>>> YuChang
>>>
>>
>> Can you please also expand on CLK_INFRA_AO_I2C{1,2,5}_ARBITER clocks?
>> Is the I2C arbiter also legacy of previous designs?
>>
>> Please check [1], as I've sent a commit adding those in the
>> devicetree.
>>
>> Thanks,
>> Angelo
>>
>> [1]:
>>
> https://lore.kernel.org/all/20231020075540.15191-1-angelogioacchino.delregno@collabora.com/
> 
> According to Hardware designer this arbiter clock is also lagecy of
> previous design and serve no function. And they are conneted to top_i2c
> as well.
> 
> top_i2c-> CLK_INFRA_AO_I2C{1,2,5}_ARBITER
> 
> Also may I know the experiment that lead to the conclusion that you
> need the ARBITER clock, and the clock tree is incorrect? I will bring
> it back to discuss with our I2C owner.
> 

I had lockups during boot and PM suspend/resume, plus, I was getting issues with
losing trackpad functionality; adding the arbiter clocks fixed the issue.

Regards,
Angelo