From 4745dc8abb0a0a9851c07265eea01d844886d5c8 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Thu, 27 Jun 2019 16:36:04 -0300 Subject: docs: phy: place documentation under driver-api This subsystem-specific documentation belongs to the driver-api. Signed-off-by: Mauro Carvalho Chehab --- Documentation/phy/samsung-usb2.rst | 137 ------------------------------------- 1 file changed, 137 deletions(-) delete mode 100644 Documentation/phy/samsung-usb2.rst (limited to 'Documentation/phy') diff --git a/Documentation/phy/samsung-usb2.rst b/Documentation/phy/samsung-usb2.rst deleted file mode 100644 index c48c8b9797b9..000000000000 --- a/Documentation/phy/samsung-usb2.rst +++ /dev/null @@ -1,137 +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. -- cgit v1.2.3