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.

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 | 16 +++++++++++++---
 3 files changed, 15 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..3d833a325c61f 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>
@@ -1115,9 +1116,15 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 						"state_uhs");
 	}
 
+	priv->mux_state = devm_mux_state_get_optional_selected(&pdev->dev, NULL);
+	if (IS_ERR(priv->mux_state))
+		return PTR_ERR(priv->mux_state);
+
 	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 +1207,7 @@ 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 +1311,9 @@ 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