Some hardware designs route data or control signals through a mux to
support multiple devices on a single sdhi 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.

SD/SDIO/eMMC are not well suited for runtime switching between different
cards, however boot-time selection is possible and useful - in
particular considering dt overlays.

Add support for an optional SD/SDIO/eMMC mux defined in dt, and select
it during probe.

Similar functionality already exists in other places, e.g. i2c-omap.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Josua Mayer <josua@solid-run.com>
---
 drivers/mmc/host/renesas_sdhi_core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
index 2a310a145785..f9ec78d699f4 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>
@@ -1062,6 +1063,7 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 	struct regulator_dev *rdev;
 	struct renesas_sdhi_dma *dma_priv;
 	struct device *dev = &pdev->dev;
+	struct mux_state *mux_state;
 	struct tmio_mmc_host *host;
 	struct renesas_sdhi *priv;
 	int num_irqs, irq, ret, i;
@@ -1116,6 +1118,10 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 						"state_uhs");
 	}
 
+	mux_state = devm_mux_state_get_optional_selected(&pdev->dev, NULL);
+	if (IS_ERR(mux_state))
+		return PTR_ERR(mux_state);
+
 	host = tmio_mmc_host_alloc(pdev, mmc_data);
 	if (IS_ERR(host))
 		return PTR_ERR(host);

-- 
2.43.0

On Tue, Feb 03, 2026 at 03:01:40PM +0200, Josua Mayer wrote:
> Some hardware designs route data or control signals through a mux to
> support multiple devices on a single sdhi 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.
> 
> SD/SDIO/eMMC are not well suited for runtime switching between different
> cards, however boot-time selection is possible and useful - in
> particular considering dt overlays.
> 
> Add support for an optional SD/SDIO/eMMC mux defined in dt, and select
> it during probe.
> 
> Similar functionality already exists in other places, e.g. i2c-omap.
> 
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Signed-off-by: Josua Mayer <josua@solid-run.com>

And to confirm the obvious, no regression found on a Renesas SparrowHawk
(R-Car V4H) not using muxes:

Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

On Tue, Feb 03, 2026 at 03:01:40PM +0200, Josua Mayer wrote:
> Some hardware designs route data or control signals through a mux to
> support multiple devices on a single sdhi 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.
> 
> SD/SDIO/eMMC are not well suited for runtime switching between different
> cards, however boot-time selection is possible and useful - in
> particular considering dt overlays.
> 
> Add support for an optional SD/SDIO/eMMC mux defined in dt, and select
> it during probe.
> 
> Similar functionality already exists in other places, e.g. i2c-omap.
> 
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Signed-off-by: Josua Mayer <josua@solid-run.com>

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>