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

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Message-ID: <808fd3ca-c3f1-46bd-a68e-514629ac07a3@solid-run.com>
Date: Wed, 10 Dec 2025 14:54:45 +0000
From: Josua Mayer <josua@...id-run.com>
To: Rob Herring <robh@...nel.org>
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"
	<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 2/2] mmc: host: renesas_sdhi_core: support configuring
 an optional sdio mux


Am 08.12.25 um 02:24 schrieb Rob Herring:
> 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.
Other drivers have so far avoided introducing a general helper for this.
Notably drivers/phy/phy-can-transceiver.c has already implemented
its own version of devm_mux_state_get_optional.
>
>> +		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?
I suppose it is always an error.
> If 
> not, mux_state_select() should do the printing.

Possibly. Except when it is EDEFER.

Inside driver we would use dev_err_probe in this case.
Should helpers do the same?

>
>> +			return ret;
>> +		}
>> +	}