linux-kernel - Re: [PATCH 1/1] riscv: dts: starfive: Milk-V Mars CM Lite broken-cd

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Message-ID: <46d5d249-8cf2-46d1-a90c-1f2c5f146e15@canonical.com>
Date: Wed, 4 Feb 2026 17:38:54 +0100
From: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
To: Emil Renner Berthing <kernel@...il.dk>, Conor Dooley <conor@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>,
 Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
 E Shattow <e@...eshell.de>, linux-riscv@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] riscv: dts: starfive: Milk-V Mars CM Lite broken-cd

On 2/4/26 11:16, Heinrich Schuchardt wrote:
> The card detect GPIO depends on support by the base board.
> 
> Detecting an SD-card did not work for me with a Milk-V Mars CM Lite
> mounted on an Waveshare CM4-IO-BASE-A board.

The schematic of the Waveshare CM4-IO-BASE-A board is available at
https://files.waveshare.com/upload/a/aa/CM4-IO-BASE-A_V4_SchDoc.pdf
showing pin 76 is not connected.

In https://forums.raspberrypi.com/viewtopic.php?t=291041 the Raspberry 
Foundation explicitly wrote that pin 76 should not be connected when 
using a compute module socket.

E. Shattow pointed me to a board
https://github.com/NabuCasa/yellow/releases/download/v1.3c/Yellow_v1.3c_Schematic_git.8957b440adda.pdf
that actually disregarded this advice and uses pin 76 actually as 
cd-gpio. This usage of GPIO 41 is a property of the specific base board 
and not of the Milk-V Mars CM and should be described in a device-tree 
overlay if needed.

Best regards

Heinrich

> 
> According to [1] SD_SDIO0_CD_GPIO41 is connected to pin 76 reserved.
> The Raspberry Pi Compute Module 4 IO Board documentation marks that pin as
> reserved. The Raspberry Pi Compute Module 5 IO Board documentation
> marks the pin as VBAT.
> 
> Remove the cd-gpios definition and add broken-cd.
> 
> [1]  https://github.com/milkv-mars/mars-files/blob/main/Mars-CM_Hardware_Schematices/Milk-V_Mars-CM_SCH_V1.0-2023-0905_Lite.pdf
> 
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
> ---
>   arch/riscv/boot/dts/starfive/jh7110-milkv-marscm-lite.dts | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/boot/dts/starfive/jh7110-milkv-marscm-lite.dts b/arch/riscv/boot/dts/starfive/jh7110-milkv-marscm-lite.dts
> index 63aa94d65ab55..566b0bdc2800d 100644
> --- a/arch/riscv/boot/dts/starfive/jh7110-milkv-marscm-lite.dts
> +++ b/arch/riscv/boot/dts/starfive/jh7110-milkv-marscm-lite.dts
> @@ -13,7 +13,7 @@ / {
>   
>   &mmc0 {
>   	bus-width = <4>;
> -	cd-gpios = <&sysgpio 41 GPIO_ACTIVE_LOW>;
> +	broken-cd;
>   	disable-wp;
>   };
>