linux-kernel - Re: [PATCH 3/9] mfd: mt6397: Split MediaTek MT6366 PMIC out of MT6358

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Date:   Fri, 4 Aug 2023 08:39:19 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chen-Yu Tsai <wenst@...omium.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Lee Jones <lee@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Zhiyong Tao <zhiyong.tao@...iatek.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 3/9] mfd: mt6397: Split MediaTek MT6366 PMIC out of MT6358

Il 04/08/23 05:47, Chen-Yu Tsai ha scritto:
> On Thu, Aug 3, 2023 at 5:01 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
>>
>> Il 03/08/23 09:42, Chen-Yu Tsai ha scritto:
>>> The MT6366 PMIC is mostly, but not fully, compatible with MT6358. It has
>>> a different set of regulators. Specifically, it lacks the camera related
>>> VCAM* LDOs, but has additional VM18, VMDDR, and VSRAM_CORE LDOs.
>>>
>>> Add a separate compatible for the MT6366 PMIC. The regulator cell for
>>> this new entry uses a new compatible string matching MT6366.
>>>
>>> Fixes: c47383f84909 ("mfd: Add support for the MediaTek MT6366 PMIC")
>>> Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
>>
>> I agree in that the LDOs are a bit different, but that's handled by the
>> mt6358-regulator driver regardless of the actual devicetree compatible,
>> as that's selected through a chip_id check.
>>
>> Finally, looking at the driver implementation itself, the addition of a
>> specific mt6366 compatible here seems redundant, because the actual HW is
>>    - Handled by drivers, but
>>    - Described by bindings
>>
>> Any other opinions on this?
> 
> Well, on the bindings side, we can't have MT6366 fall back to MT6358,
> neither for the whole PMIC nor just for the regulators. For the latter
> it's because neither is a subset of the other, which a) makes them not
> fallback compatible as required by the spirit of fallback compatibles,
> and b) cannot be described with a fallback compatible, as the fallback
> one will have properties/nodes that are not valid for the other, and
> vice versa.
> 
> Without a fallback compatible to lean in for the regulator driver, we
> will need to split out the compatible at the mfd level as well. AFAIU
> the mfd core matches mfd-cells based on the compatible strings it is
> given in the driver.
> 

Hmm... you might actually be right on this.
But! I just want to be sure that we're doing things the right way.. and
I'd like to get an opinion from a bindings person, as I think that's the
most appropriate thing that can be done.

Krzysztof, please, can you check this one?

Thanks!
Angelo

> ChenYu
> 
>> Regards,
>> Angelo
>>
>>> ---
>>>    drivers/mfd/mt6397-core.c | 31 +++++++++++++++++++++++++++++++
>>>    1 file changed, 31 insertions(+)
>>>
>>> diff --git a/drivers/mfd/mt6397-core.c b/drivers/mfd/mt6397-core.c
>>> index f6c1f80f94a4..3f8dfe60a59b 100644
>>> --- a/drivers/mfd/mt6397-core.c
>>> +++ b/drivers/mfd/mt6397-core.c
>>> @@ -206,6 +206,26 @@ static const struct mfd_cell mt6359_devs[] = {
>>>        },
>>>    };
>>>
>>> +static const struct mfd_cell mt6366_devs[] = {
>>> +     {
>>> +             .name = "mt6358-regulator",
>>> +             .of_compatible = "mediatek,mt6366-regulator"
>>> +     }, {
>>> +             .name = "mt6358-rtc",
>>> +             .num_resources = ARRAY_SIZE(mt6358_rtc_resources),
>>> +             .resources = mt6358_rtc_resources,
>>> +             .of_compatible = "mediatek,mt6358-rtc",
>>> +     }, {
>>> +             .name = "mt6358-sound",
>>> +             .of_compatible = "mediatek,mt6358-sound"
>>> +     }, {
>>> +             .name = "mt6358-keys",
>>> +             .num_resources = ARRAY_SIZE(mt6358_keys_resources),
>>> +             .resources = mt6358_keys_resources,
>>> +             .of_compatible = "mediatek,mt6358-keys"
>>> +     },
>>> +};
>>> +
>>>    static const struct mfd_cell mt6397_devs[] = {
>>>        {
>>>                .name = "mt6397-rtc",
>>> @@ -280,6 +300,14 @@ static const struct chip_data mt6359_core = {
>>>        .irq_init = mt6358_irq_init,
>>>    };
>>>
>>> +static const struct chip_data mt6366_core = {
>>> +     .cid_addr = MT6358_SWCID,
>>> +     .cid_shift = 8,
>>> +     .cells = mt6366_devs,
>>> +     .cell_size = ARRAY_SIZE(mt6366_devs),
>>> +     .irq_init = mt6358_irq_init,
>>> +};
>>> +
>>>    static const struct chip_data mt6397_core = {
>>>        .cid_addr = MT6397_CID,
>>>        .cid_shift = 0,
>>> @@ -358,6 +386,9 @@ static const struct of_device_id mt6397_of_match[] = {
>>>        }, {
>>>                .compatible = "mediatek,mt6359",
>>>                .data = &mt6359_core,
>>> +     }, {
>>> +             .compatible = "mediatek,mt6366",
>>> +             .data = &mt6366_core,
>>>        }, {
>>>                .compatible = "mediatek,mt6397",
>>>                .data = &mt6397_core,
>>
>>