ACK: [SRU][Q:raspi/N:raspi][PATCH 0/1] RP1's sdio controller requires sdhci-of-dwcmshc driver (LP: #2136415)

[Tim Whisonant]

On Mon, Jan 12, 2026 at 12:01:54PM +0100, Juerg Haefliger wrote:
> BugLink: https://bugs.launchpad.net/bugs/2136415
> 
> [ Impact ]
> 
> Summary:
> ----------------
> The kernel config `CONFIG_MMC_SDHCI_OF_DWCMSHC` is not enabled. This is required by the RP1 peripheral controller so that the Raspberry Pi 5 leverages the SDIO bus.
> 
> Description:
> ----------------
> 
> The SD card attached to a Raspberry Pi Compute Module 5 via GPIOs 22-27 is not working properly, although the `sdio` / `sdio-pi5` overlay is present. In Raspberry Pi OS, everything works fine. I tried different kernels, distros, and configurations. I found out that the overlay loads, the clocks appear, but no MMC host binds. Finally, I discovered that the driver `CONFIG_MMC_SDHCI_OF_DWCMSHC` is not enabled in the Ubuntu kernel for Raspberry Pi devices, which is necessary for the RP1 SDIO controller.
> 
> Evidence:
> ----------------
> The `rp1_mmc0` and `rp1_mmc1` nodes in RP1 dtsi (arch/arm64/boot/dts/broadcom/rp1.dtsi) are compatible with `raspberrypi,rp1-dwcmshc`. This is implemented by the `sdhci-of-dwcmshc` driver (drivers/mmc/host/sdhci-of-dwcmshc.c) and enabled by the kernel config `CONFIG_MMC_SDHCI_OF_DWCMSHC`.
> Furthermore, the RP1 datasheet states that the `SDIO controller is a Synopsys MSHC peripheral v1.70a`.
> 
> Hardware:
> ----------------
> - Raspberry Pi 5
> - Raspberry Pi Compute Module 5
> 
> Ubuntu release:
> ----------------
> Description:	Ubuntu 24.04.3 LTS
> Release:	24.04
> 
> Package affected:
> ----------------
> linux-raspi:
>   Installed: (none)
>   Candidate: 6.8.0-1043.47
>   Version table:
>      6.8.0-1043.47 500
>         500 http://ports.ubuntu.com/ubuntu-ports noble-updates/main arm64 Packages
>         500 http://ports.ubuntu.com/ubuntu-ports noble-security/main arm64 Packages
>      6.8.0-1004.4 500
>         500 http://ports.ubuntu.com/ubuntu-ports noble/main arm64 Packages
> 
> Proposed fix:
> ----------------
> Set the kernel config `CONFIG_MMC_SDHCI_OF_DWCMSHC` to module by default. Patch attached.
> 
> Others:
> ----------------
> - https://forums.raspberrypi.com/viewtopic.php?t=392105
> 
> [ Fix ]
> 
> Remove raspi annotations that disable the option.
> 
> [ Test Case ]
> 
> Verify module sdhci-of-dwcmshc.ko exists and is functional.
> 
> [ Where Problems Could Occur ]
> 
> This enables new modules which - as always with kernel - can crash/stall/hang a system when loaded. Should only affect systems that have the HW that needs the new module(s).
> 
> Juerg Haefliger (1):
>   UBUNTU: [Config] raspi: Don't disable MMC_SDHCI_OF_DWCMSHC
> 
>  debian.raspi/config/annotations | 1 -
>  1 file changed, 1 deletion(-)
> 
> -- 
> 2.51.0
> 
> 

Acked-by: Tim Whisonant <tim.whisonant at canonical.com>