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

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Message-ID: <20240821110940.s5ubbcozk2bouklh@chaps>
Date: Wed, 21 Aug 2024 06:09:40 -0500
From: Nishanth Menon <nm@...com>
To: Bjorn Andersson <quic_bjorande@...cinc.com>
CC: Judith Mendez <jm@...com>, 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>
Subject: Re: [RFC PATCH] arm64: defconfig: Set MFD_TPS6594_I2C as built-in

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

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D