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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:
Mauro Carvalho Chehab 2019-04-15 19:27:55 -03:00
parent a278295ccc
commit 1945a03554
2 changed files with 34 additions and 30 deletions
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62
Documentation/phy/samsung-usb2.txt → Documentation/phy/samsung-usb2.rst
View File

@ -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.

2
MAINTAINERS
View File

@ -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