linux-kernel - Re: [RFC PATCH] arm64: defconfig: Set MFD_TPS6594

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Message-ID: <8119c948-5609-4f61-bf49-aaaf82cd9597@ti.com>
Date: Thu, 26 Sep 2024 15:10:38 -0500
From: Judith Mendez <jm@...com>
To: Nishanth Menon <nm@...com>
CC: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Dmitry Baryshkov
	<dmitry.baryshkov@...aro.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski@...aro.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        Vignesh Raghavendra <vigneshr@...com>, Bryan Brattlof <bb@...com>,
        Bjorn
 Andersson <quic_bjorande@...cinc.com>
Subject: Re: [RFC PATCH] arm64: defconfig: Set MFD_TPS6594_I2C as built-in

Hi Nishanth,

On 8/21/24 6:09 AM, Nishanth Menon wrote:
> On 09:42-20240820, Bjorn Andersson wrote:
>> On Mon, Aug 19, 2024 at 03:43:52PM -0500, Judith Mendez wrote:
>>> SK-AM62A-LP is a device targeting automotive front-camera applications
>>> among other use-cases. It utilizes the TPS6593x PMIC (interfaced over I2C)
>>> to power the SoC and various other peripherals on the board [1].
>>>
>>> MMCSD requires the PMIC to be setup correctly before setting the bus
>>> pins to 1.8V using the TPS6594 driver interfaced over i2c.
>>>
>>> Currently, the following could be seen when booting the am62ax platform:
>>>
>>> "platform fa00000.mmc: deferred probe pending: platform: supplier regulator-5 not ready"
>>> "vdd_mmc1: disabling"
>>
>> Is this the regulator framework disabling the "unused" vdd_mmc1 while
>> you still have a probe deferred client?
>>
>> That's not right.
> 
> I think context of the full log might be missing, hence misleading - but
> if this is correct, regulator framework might have a problem as well -
> it does not change the fact that we will need regulator driver to
> support switch from 3.3v to 1.8v to enable UHS (which is another
> topic as well - do not trust the bootloader either for the default
> voltage enabled in the system).
> 
> Judith: This is why providing links to previous versions of patches AND
> providing links to the full before and after logs in the diffstat
> section helps reviewers - please do that in the next revision.
> 
>>
>>>
>>> and a failure to boot the SK-AM62A-LP.
>>>
>>> One solution is to use initramfs [2], but using initramfs increases the
>>> boot time for this automotive solution which requires faster boot time
>>> parameters.
>>>
>>> Another solution is to change MFD_TPS6594_I2C to built-in, that way the
>>> PMIC is setup and the regulators are ready before MMCSD switches to UHS
>>> mode, this is the preferred solution since it does not increase boot time
>>> like the initramfs solution does.
> 
> What is the adder in cost? bloat-o-meter report summary should have
> been part of commits that increase vmlinux
> 
>>>
>>> [1] https://www.ti.com/lit/zip/sprr459
>>> [2] https://lore.kernel.org/linux-devicetree/5f03207b-c29b-4d16-92b0-d14eef77bf17@linaro.org/
>>> Fixes: f9010eb938be ("arm64: defconfig: Enable TPS6593 PMIC for SK-AM62A")
>>>
>>> Signed-off-by: Judith Mendez <jm@...com>
>>> ---
>>>   arch/arm64/configs/defconfig | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
>>> index 7d32fca649965..61f767246d3a5 100644
>>> --- a/arch/arm64/configs/defconfig
>>> +++ b/arch/arm64/configs/defconfig
>>> @@ -756,7 +756,7 @@ CONFIG_RZ_MTU3=y
>>>   CONFIG_MFD_TI_AM335X_TSCADC=m
>>>   CONFIG_MFD_TI_LP873X=m
>>>   CONFIG_MFD_TPS65219=y
>>> -CONFIG_MFD_TPS6594_I2C=m
>>> +CONFIG_MFD_TPS6594_I2C=y
>>
>> These things should work with =m, and then you can make them =y in your
>> product config to avoid the probe deferral.
> 
> I think this is inline with the discussion with Krystoff on the topic as
> well
> 
> 
> Judith: you just need the regulator, for sd/mmc to work. Why is there
> half a dozen unrelated stuff coming with it [1] report from
> bloat-o-meter? Please fix the driver dependencies before adding
> un-necessary stuff to the kernel Image file.
> 
> [1] https://gist.github.com/nmenon/0caff032a430bbf649ad1107e6f12f9a


It seems like TPS6594_I2C driver has a few dependencies:

select MFD_TPS6594
select REGMAP_I2C
select CRC8
depends on I2C

I am not sure what could be done here to change the driver to built
in without increasing the size of the kernel this much:

Total: Before=19064141, After=19108349, chg +0.23%

Please advice.
Thanks,

~ Judith