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

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Message-ID: <1a7def3f-a19c-4f1c-845c-a3854c165995@linaro.org>
Date: Mon, 19 Aug 2024 23:01:26 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Judith Mendez <jm@...com>, Catalin Marinas <catalin.marinas@....com>,
 Will Deacon <will@...nel.org>
Cc: Bjorn Andersson <quic_bjorande@...cinc.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Bryan Brattlof <bb@...com>
Subject: Re: [RFC PATCH] arm64: defconfig: Set MFD_TPS6594_I2C as built-in

On 19/08/2024 22:43, 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"
> 
> 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.

This is a defconfig, not a distro/product config, so your product
constraints are not really relevant. You are supposed to boot defconfig
with proper initramfs with necessary modules.

I don't get why people mistake defconfig with their product stuff...

> 
> 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.

Use initramfs. Several devices, e.g. most Android ones, have fixed size
of boot partition, so size of kernel is important.

> 
> [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")

No bug here to be fixed. You miss initramfs.

> 
> Signed-off-by: Judith Mendez <jm@...com>


Best regards,
Krzysztof