linux-kernel - Re: [PATCH v2 0/2] mmc: host: renesas_sdhi_core: support configuring an optional sdio mux

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Message-ID: <af4da0ac-a6f3-4248-9050-537a4ecf7711@solid-run.com>
Date: Mon, 1 Dec 2025 14:21:18 +0000
From: Josua Mayer <josua@...id-run.com>
To: Biju Das <biju.das.jz@...renesas.com>, Ulf Hansson
	<ulf.hansson@...aro.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
	<krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Geert Uytterhoeven
	<geert+renesas@...der.be>, magnus.damm <magnus.damm@...il.com>, wsa+renesas
	<wsa+renesas@...g-engineering.com>
CC: Mikhail Anikin <mikhail.anikin@...id-run.com>, Yazan Shhady
	<yazan.shhady@...id-run.com>, Jon Nettleton <jon@...id-run.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] mmc: host: renesas_sdhi_core: support configuring
 an optional sdio mux

Am 01.12.25 um 14:17 schrieb Biju Das:
>
>> -----Original Message-----
>> From: Josua Mayer <josua@...id-run.com>
>> Sent: 01 December 2025 12:31
>> Subject: [PATCH v2 0/2] mmc: host: renesas_sdhi_core: support configuring an optional sdio mux
>>
>> Some Renesas SoC based boards mux SD and eMMC on a single sdio controller, exposing user control by
>> dip switch and software control by gpio.
>>
>> Purpose is to simplify development and provisioning by selecting boot media at power-on, and again
>> before starting linux.
> Does it mean, you boot with eSD mode, boot the linux with SD mode and flash the image to eMMC??
>
> and then, switch to eMMC boot mode and boot everything from eMMC??
>
>
> Or
>
> boot with eSD mode, flash emmc images at initramfs level/u-boot level
>
> and then, switch to eMMC boot mode and boot everything from eMMC??

The latter.

DIP switch decides bootloader starting from eMMC or SD.
Then u-boot has complete freedom.

Finally U-Boot shall load (and patch) DTB for either eMMC or SD.
Regardless of whether rootfs is initramfs or physical media.