phy: Add new Exynos USB 2.0 PHY driver

Add a new driver for the Exynos USB 2.0 PHY. The new driver uses the generic
PHY framework. The driver includes support for the Exynos 4x10 and 4x12
SoC families.

Signed-off-by: Kamil Debski <k.debski@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

2 files changed, 188 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/phy/samsung-phy.txt b/Documentation/devicetree/bindings/phy/samsung-phy.txt
index c0fccaa1671e..bf955abba5d9 100644
--- a/Documentation/devicetree/bindings/phy/samsung-phy.txt
+++ b/Documentation/devicetree/bindings/phy/samsung-phy.txt
@@ -20,3 +20,56 @@ Required properties:
 - compatible : should be "samsung,exynos5250-dp-video-phy";
 - reg : offset and length of the Display Port PHY register set;
 - #phy-cells : from the generic PHY bindings, must be 0;
+
+Samsung S5P/EXYNOS SoC series USB PHY
+-------------------------------------------------
+
+Required properties:
+- compatible : should be one of the listed compatibles:
+	- "samsung,exynos4210-usb2-phy"
+	- "samsung,exynos4x12-usb2-phy"
+- reg : a list of registers used by phy driver
+	- first and obligatory is the location of phy modules registers
+- samsung,sysreg-phandle - handle to syscon used to control the system registers
+- samsung,pmureg-phandle - handle to syscon used to control PMU registers
+- #phy-cells : from the generic phy bindings, must be 1;
+- clocks and clock-names:
+	- the "phy" clock is required by the phy module, used as a gate
+	- the "ref" clock is used to get the rate of the clock provided to the
+	  PHY module
+
+The first phandle argument in the PHY specifier identifies the PHY, its
+meaning is compatible dependent. For the currently supported SoCs (Exynos 4210
+and Exynos 4212) it is as follows:
+  0 - USB device ("device"),
+  1 - USB host ("host"),
+  2 - HSIC0 ("hsic0"),
+  3 - HSIC1 ("hsic1"),
+
+Exynos 4210 and Exynos 4212 use mode switching and require that mode switch
+register is supplied.
+
+Example:
+
+For Exynos 4412 (compatible with Exynos 4212):
+
+usbphy: phy@125b0000 {
+	compatible = "samsung,exynos4x12-usb2-phy";
+	reg = <0x125b0000 0x100>;
+	clocks = <&clock 305>, <&clock 2>;
+	clock-names = "phy", "ref";
+	status = "okay";
+	#phy-cells = <1>;
+	samsung,sysreg-phandle = <&sys_reg>;
+	samsung,pmureg-phandle = <&pmu_reg>;
+};
+
+Then the PHY can be used in other nodes such as:
+
+phy-consumer@12340000 {
+	phys = <&usbphy 2>;
+	phy-names = "phy";
+};
+
+Refer to DT bindings documentation of particular PHY consumer devices for more
+information about required PHYs and the way of specification.
diff --git a/Documentation/phy/samsung-usb2.txt b/Documentation/phy/samsung-usb2.txt
new file mode 100644
index 000000000000..ed12d437189d
--- /dev/null
+++ b/Documentation/phy/samsung-usb2.txt
@@ -0,0 +1,135 @@
+.------------------------------------------------------------------------------+
+|			Samsung USB 2.0 PHY adaptation layer		       |
++-----------------------------------------------------------------------------+'
+
+| 1. Description
++----------------
+
+The architecture of the USB 2.0 PHY module in Samsung SoCs is similar
+among many SoCs. In spite of the similarities it proved difficult to
+create a one driver that would fit all these PHY controllers. Often
+the differences were minor and were found in particular bits of the
+registers of the PHY. In some rare cases the order of register writes or
+the PHY powering up process had to be altered. This adaptation layer is
+a compromise between having separate drivers and having a single driver
+with added support for many special cases.
+
+| 2. Files description
++----------------------
+
+- phy-samsung-usb2.c
+   This is the main file of the adaptation layer. This file contains
+   the probe function and provides two callbacks to the Generic PHY
+   Framework. This two callbacks are used to power on and power off the
+   phy. They carry out the common work that has to be done on all version
+   of the PHY module. Depending on which SoC was chosen they execute SoC
+   specific callbacks. The specific SoC version is selected by choosing
+   the appropriate compatible string. In addition, this file contains
+   struct of_device_id definitions for particular SoCs.
+
+- phy-samsung-usb2.h
+   This is the include file. It declares the structures used by this
+   driver. In addition it should contain extern declarations for
+   structures that describe particular SoCs.
+
+| 3. Supporting SoCs
++--------------------
+
+To support a new SoC a new file should be added to the drivers/phy
+directory. Each SoC's configuration is stored in an instance of the
+struct samsung_usb2_phy_config.
+
+struct samsung_usb2_phy_config {
+	const struct samsung_usb2_common_phy *phys;
+	int (*rate_to_clk)(unsigned long, u32 *);
+	unsigned int num_phys;
+	bool has_mode_switch;
+};
+
+The num_phys is the number of phys handled by the driver. *phys is an
+array that contains the configuration for each phy. The has_mode_switch
+property is a boolean flag that determines whether the SoC has USB host
+and device on a single pair of pins. If so, a special register has to
+be modified to change the internal routing of these pins between a USB
+device or host module.
+
+For example the configuration for Exynos 4210 is following:
+
+const struct samsung_usb2_phy_config exynos4210_usb2_phy_config = {
+	.has_mode_switch        = 0,
+	.num_phys		= EXYNOS4210_NUM_PHYS,
+	.phys			= exynos4210_phys,
+	.rate_to_clk		= exynos4210_rate_to_clk,
+}
+
+- int (*rate_to_clk)(unsigned long, u32 *)
+	The rate_to_clk callback is to convert the rate of the clock
+	used as the reference clock for the PHY module to the value
+	that should be written in the hardware register.
+
+The exynos4210_phys configuration array is as follows:
+
+static const struct samsung_usb2_common_phy exynos4210_phys[] = {
+	{
+		.label		= "device",
+		.id		= EXYNOS4210_DEVICE,
+		.power_on	= exynos4210_power_on,
+		.power_off	= exynos4210_power_off,
+	},
+	{
+		.label		= "host",
+		.id		= EXYNOS4210_HOST,
+		.power_on	= exynos4210_power_on,
+		.power_off	= exynos4210_power_off,
+	},
+	{
+		.label		= "hsic0",
+		.id		= EXYNOS4210_HSIC0,
+		.power_on	= exynos4210_power_on,
+		.power_off	= exynos4210_power_off,
+	},
+	{
+		.label		= "hsic1",
+		.id		= EXYNOS4210_HSIC1,
+		.power_on	= exynos4210_power_on,
+		.power_off	= exynos4210_power_off,
+	},
+	{},
+};
+
+- int (*power_on)(struct samsung_usb2_phy_instance *);
+- int (*power_off)(struct samsung_usb2_phy_instance *);
+	These two callbacks are used to power on and power off the phy
+	by modifying appropriate registers.
+
+Final change to the driver is adding appropriate compatible value to the
+phy-samsung-usb2.c file. In case of Exynos 4210 the following lines were
+added to the struct of_device_id samsung_usb2_phy_of_match[] array:
+
+#ifdef CONFIG_PHY_EXYNOS4210_USB2
+	{
+		.compatible = "samsung,exynos4210-usb2-phy",
+		.data = &exynos4210_usb2_phy_config,
+	},
+#endif
+
+To add further flexibility to the driver the Kconfig file enables to
+include support for selected SoCs in the compiled driver. The Kconfig
+entry for Exynos 4210 is following:
+
+config PHY_EXYNOS4210_USB2
+	bool "Support for Exynos 4210"
+	depends on PHY_SAMSUNG_USB2
+	depends on CPU_EXYNOS4210
+	help
+	  Enable USB PHY support for Exynos 4210. This option requires that
+	  Samsung USB 2.0 PHY driver is enabled and means that support for this
+	  particular SoC is compiled in the driver. In case of Exynos 4210 four
+	  phys are available - device, host, HSCI0 and HSCI1.
+
+The newly created file that supports the new SoC has to be also added to the
+Makefile. In case of Exynos 4210 the added line is following:
+
+obj-$(CONFIG_PHY_EXYNOS4210_USB2)       += phy-exynos4210-usb2.o
+
+After completing these steps the support for the new SoC should be ready.