aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/phy/samsung-usb2.txt
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/phy/samsung-usb2.txt')
-rw-r--r--Documentation/phy/samsung-usb2.txt135
1 files changed, 0 insertions, 135 deletions
diff --git a/Documentation/phy/samsung-usb2.txt b/Documentation/phy/samsung-usb2.txt
deleted file mode 100644
index ed12d437189d..000000000000
--- a/Documentation/phy/samsung-usb2.txt
+++ /dev/null
@@ -1,135 +0,0 @@
-.------------------------------------------------------------------------------+
-| 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.