BCM270X_DT: Add SDIO overlay

Enable SDIO from MMC interface via GPIOs 22-27. Includes the sdhost
overlay to free up the MMC interface.

Author: Phil Elwell

arch/arm/boot/dts/overlays/Makefile

@@ -44,6 +44,7 @@ dtb-$(RPI_DT_OVERLAYS) += rpi-ft5406-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += rpi-proto-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += rpi-sense-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += sdhost-overlay.dtb
+dtb-$(RPI_DT_OVERLAYS) += sdio-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += spi-bcm2708-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += spi-bcm2835-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += spi-dma-overlay.dtb

arch/arm/boot/dts/overlays/README

@@ -513,6 +513,21 @@ Params: overclock_50             Clock (in MHz) to use when the MMC framework
         debug                    Enable debug output (default off)
 
 
+Name:   sdio
+Info:   Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
+        and enables SDIO via GPIOs 22-27.
+Load:   dtoverlay=sdio,<param>=<val>
+Params: overclock_50             Clock (in MHz) to use when the MMC framework
+                                 requests 50MHz
+
+        force_pio                Disable DMA support (default off)
+
+        pio_limit                Number of blocks above which to use DMA
+                                 (default 1)
+
+        debug                    Enable debug output (default off)
+
+
 Name:   spi-bcm2708
 Info:   Selects the bcm2708-spi SPI driver
 Load:   dtoverlay=spi-bcm2708

arch/arm/boot/dts/overlays/sdio-overlay.dts

@@ -0,0 +1,29 @@
+/* Enable SDIO from MMC interface via GPIOs 22-27. Includes sdhost overlay. */
+
+/include/ "sdhost-overlay.dts"
+
+/{
+	compatible = "brcm,bcm2708";
+
+	fragment@3 {
+		target = <&mmc>;
+		__overlay__ {
+			compatible = "brcm,bcm2835-mmc";
+			pinctrl-names = "default";
+			pinctrl-0 = <&sdio_pins>;
+			non-removable;
+			status = "okay";
+		};
+	};
+
+	fragment@4 {
+		target = <&gpio>;
+		__overlay__ {
+			sdio_pins: sdio_pins {
+				brcm,pins = <22 23 24 25 26 27>;
+				brcm,function = <7 7 7 7 7 7>; /* ALT3 = SD1 */
+				brcm,pull = <0 2 2 2 2 2>;
+			};
+		};
+	};
+};