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@solid-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);
+		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);
+			return ret;
+		}
+	}
+
 	host = tmio_mmc_host_alloc(pdev, mmc_data);
-	if (IS_ERR(host))
-		return PTR_ERR(host);
+	if (IS_ERR(host)) {
+		ret = PTR_ERR(host);
+		goto edselmux;
+	}
 
 	priv->host = host;
 
@@ -1200,7 +1218,7 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 
 	ret = renesas_sdhi_clk_enable(host);
 	if (ret)
-		return ret;
+		goto edselmux;
 
 	rcfg.of_node = of_get_available_child_by_name(dev->of_node, "vqmmc-regulator");
 	if (rcfg.of_node) {
@@ -1304,6 +1322,9 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 
 edisclk:
 	renesas_sdhi_clk_disable(host);
+edselmux:
+	if (priv->mux_state)
+		mux_state_deselect(priv->mux_state);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(renesas_sdhi_probe);

-- 
2.51.0