mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-28 20:02:17 +00:00
docs: phy: convert samsung-usb2.txt to ReST format
In order to merge it into a Sphinx book, we need first to convert to ReST. While this is not part of any book, mark it as :orphan:, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
This commit is contained in:
parent
a278295ccc
commit
1945a03554
2 changed files with 34 additions and 30 deletions
|
@ -1,9 +1,11 @@
|
|||
.------------------------------------------------------------------------------+
|
||||
| Samsung USB 2.0 PHY adaptation layer |
|
||||
+-----------------------------------------------------------------------------+'
|
||||
:orphan:
|
||||
|
||||
| 1. Description
|
||||
+----------------
|
||||
====================================
|
||||
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
|
||||
|
@ -14,8 +16,8 @@ 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
|
||||
+----------------------
|
||||
2. Files description
|
||||
--------------------
|
||||
|
||||
- phy-samsung-usb2.c
|
||||
This is the main file of the adaptation layer. This file contains
|
||||
|
@ -32,44 +34,45 @@ with added support for many special cases.
|
|||
driver. In addition it should contain extern declarations for
|
||||
structures that describe particular SoCs.
|
||||
|
||||
| 3. Supporting 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::
|
||||
|
||||
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
|
||||
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:
|
||||
For example the configuration for Exynos 4210 is following::
|
||||
|
||||
const struct samsung_usb2_phy_config exynos4210_usb2_phy_config = {
|
||||
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 *)`
|
||||
|
||||
- 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:
|
||||
The exynos4210_phys configuration array is as follows::
|
||||
|
||||
static const struct samsung_usb2_common_phy exynos4210_phys[] = {
|
||||
static const struct samsung_usb2_common_phy exynos4210_phys[] = {
|
||||
{
|
||||
.label = "device",
|
||||
.id = EXYNOS4210_DEVICE,
|
||||
|
@ -95,29 +98,30 @@ static const struct samsung_usb2_common_phy exynos4210_phys[] = {
|
|||
.power_off = exynos4210_power_off,
|
||||
},
|
||||
{},
|
||||
};
|
||||
};
|
||||
|
||||
- `int (*power_on)(struct samsung_usb2_phy_instance *);`
|
||||
`int (*power_off)(struct samsung_usb2_phy_instance *);`
|
||||
|
||||
- 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:
|
||||
added to the struct of_device_id samsung_usb2_phy_of_match[] array::
|
||||
|
||||
#ifdef CONFIG_PHY_EXYNOS4210_USB2
|
||||
#ifdef CONFIG_PHY_EXYNOS4210_USB2
|
||||
{
|
||||
.compatible = "samsung,exynos4210-usb2-phy",
|
||||
.data = &exynos4210_usb2_phy_config,
|
||||
},
|
||||
#endif
|
||||
#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:
|
||||
entry for Exynos 4210 is following::
|
||||
|
||||
config PHY_EXYNOS4210_USB2
|
||||
config PHY_EXYNOS4210_USB2
|
||||
bool "Support for Exynos 4210"
|
||||
depends on PHY_SAMSUNG_USB2
|
||||
depends on CPU_EXYNOS4210
|
||||
|
@ -128,8 +132,8 @@ config PHY_EXYNOS4210_USB2
|
|||
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:
|
||||
Makefile. In case of Exynos 4210 the added line is following::
|
||||
|
||||
obj-$(CONFIG_PHY_EXYNOS4210_USB2) += phy-exynos4210-usb2.o
|
||||
obj-$(CONFIG_PHY_EXYNOS4210_USB2) += phy-exynos4210-usb2.o
|
||||
|
||||
After completing these steps the support for the new SoC should be ready.
|
|
@ -14083,7 +14083,7 @@ M: Sylwester Nawrocki <s.nawrocki@samsung.com>
|
|||
L: linux-kernel@vger.kernel.org
|
||||
S: Supported
|
||||
F: Documentation/devicetree/bindings/phy/samsung-phy.txt
|
||||
F: Documentation/phy/samsung-usb2.txt
|
||||
F: Documentation/phy/samsung-usb2.rst
|
||||
F: drivers/phy/samsung/phy-exynos4210-usb2.c
|
||||
F: drivers/phy/samsung/phy-exynos4x12-usb2.c
|
||||
F: drivers/phy/samsung/phy-exynos5250-usb2.c
|
||||
|
|
Loading…
Reference in a new issue