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

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Message-ID: <20251208012453.GA333127-robh@kernel.org>
Date: Sun, 7 Dec 2025 19:24:53 -0600
From: Rob Herring <robh@...nel.org>
To: Josua Mayer <josua@...id-run.com>
Cc: Ulf Hansson <ulf.hansson@...aro.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>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	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,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mmc: host: renesas_sdhi_core: support configuring
 an optional sdio mux

On Mon, Dec 01, 2025 at 01:31:11PM +0100, Josua Mayer wrote:
> Some hardware designs route sdio signals through a mux to support
> multiple devices on a single sdio controller.
> In particular SolidRun RZ/G2L/G2LC/V2L System on Module use a mux for
> switching between soldered eMMC and an optional microSD on a carrier
> board, e.g. for development or provisioning.
> 
> SDIO is not well suited for runtime switching between different cards,
> however boot-time selection is possible and useful in particular with dt
> overlays.
> 
> Add support for an optional sdio mux defined in dt and select it during
> probe.
> 
> Similar functionality already exists in other places, e.g. i2c-omap.
> 
> Signed-off-by: Josua Mayer <josua@...id-run.com>
> ---
>  drivers/mmc/host/Kconfig             |  1 +
>  drivers/mmc/host/renesas_sdhi.h      |  1 +
>  drivers/mmc/host/renesas_sdhi_core.c | 27 ++++++++++++++++++++++++---
>  3 files changed, 26 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> index 2c963cb6724b9..c01ab7d81a5af 100644
> --- a/drivers/mmc/host/Kconfig
> +++ b/drivers/mmc/host/Kconfig
> @@ -707,6 +707,7 @@ config MMC_SDHI
>  	depends on SUPERH || ARCH_RENESAS || COMPILE_TEST
>  	depends on (RESET_CONTROLLER && REGULATOR) || !OF
>  	select MMC_TMIO_CORE
> +	select MULTIPLEXER
>  	help
>  	  This provides support for the SDHI SD/SDIO controller found in
>  	  Renesas SuperH, ARM and ARM64 based SoCs
> diff --git a/drivers/mmc/host/renesas_sdhi.h b/drivers/mmc/host/renesas_sdhi.h
> index 084964cecf9d8..9508908d8179f 100644
> --- a/drivers/mmc/host/renesas_sdhi.h
> +++ b/drivers/mmc/host/renesas_sdhi.h
> @@ -97,6 +97,7 @@ struct renesas_sdhi {
>  	struct reset_control *rstc;
>  	struct tmio_mmc_host *host;
>  	struct regulator_dev *rdev;
> +	struct mux_state *mux_state;
>  };
>  
>  #define host_to_priv(host) \
> diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
> index f56fa2cd208dd..c58f412ea2028 100644
> --- a/drivers/mmc/host/renesas_sdhi_core.c
> +++ b/drivers/mmc/host/renesas_sdhi_core.c
> @@ -26,6 +26,7 @@
>  #include <linux/mmc/mmc.h>
>  #include <linux/mmc/slot-gpio.h>
>  #include <linux/module.h>
> +#include <linux/mux/consumer.h>
>  #include <linux/pinctrl/consumer.h>
>  #include <linux/pinctrl/pinctrl-state.h>
>  #include <linux/platform_data/tmio.h>
> @@ -1061,6 +1062,7 @@ int renesas_sdhi_probe(struct platform_device *pdev,
>  	struct regulator_dev *rdev;
>  	struct renesas_sdhi_dma *dma_priv;
>  	struct device *dev = &pdev->dev;
> +	struct device_node *node = pdev->dev.of_node;
>  	struct tmio_mmc_host *host;
>  	struct renesas_sdhi *priv;
>  	int num_irqs, irq, ret, i;
> @@ -1115,9 +1117,25 @@ int renesas_sdhi_probe(struct platform_device *pdev,
>  						"state_uhs");
>  	}
>  
> +	if (of_property_present(node, "mux-states")) {
> +		priv->mux_state = devm_mux_state_get(&pdev->dev, NULL);

These 2 lines are really just devm_mux_state_get_optional(). Add it if 
it doesn't exist.

> +		if (IS_ERR(priv->mux_state)) {
> +			ret = PTR_ERR(priv->mux_state);
> +			dev_dbg(&pdev->dev, "failed to get SDIO mux: %d\n", ret);
> +			return ret;
> +		}
> +		ret = mux_state_select(priv->mux_state);
> +		if (ret) {
> +			dev_err(&pdev->dev, "failed to select SDIO mux: %d\n", ret);

Is there a case where mux_state_select() failing is not an error? If 
not, mux_state_select() should do the printing.

> +			return ret;
> +		}
> +	}