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dt-bindings: gpio: alignment with kernel v5.3

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Update the binding file for gpio, it is just an alignment
with kernel v5.3.
The U-Boot code example for gpio-hog (not directly linked
to binding) is moved in a new file doc/README.gpio.
[commit 21676b706e99 ("gpio: fixes for gpio-hog support")
& 'commit 4762a9988ede ("gpio: add gpio-hog support")']

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Patrick Delaunay 2020-01-13 11:35:10 +01:00 committed by Tom Rini
parent 8fd9daf036
commit 6a0388c5b1
2 changed files with 192 additions and 122 deletions
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42
doc/README.gpio Normal file
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@ -0,0 +1,42 @@
GPIO hog (CONFIG_GPIO_HOG)
--------
All the GPIO hog are initialized in gpio_hog_probe_all() function called in
board_r.c just before board_late_init() but you can also acces directly to
the gpio with gpio_hog_lookup_name().
Example, for the device tree:
tca6416@20 {
compatible = "ti,tca6416";
reg = <0x20>;
#gpio-cells = <2>;
gpio-controller;
env_reset {
gpio-hog;
input;
gpios = <6 GPIO_ACTIVE_LOW>;
};
boot_rescue {
gpio-hog;
input;
line-name = "foo-bar-gpio";
gpios = <7 GPIO_ACTIVE_LOW>;
};
};
You can than access the gpio in your board code with:
struct gpio_desc *desc;
int ret;
ret = gpio_hog_lookup_name("boot_rescue", &desc);
if (ret)
return;
if (dm_gpio_get_value(desc) == 1)
printf("\nBooting into Rescue System\n");
else if (dm_gpio_get_value(desc) == 0)
printf("\nBoot normal\n");

272
doc/device-tree-bindings/gpio/gpio.txt
View File

@ -4,19 +4,12 @@ Specifying GPIO information for devices
1) gpios property
-----------------
Nodes that makes use of GPIOs should specify them using one or more
properties, each containing a 'gpio-list':
gpio-list ::= <single-gpio> [gpio-list]
single-gpio ::= <gpio-phandle> <gpio-specifier>
gpio-phandle : phandle to gpio controller node
gpio-specifier : Array of #gpio-cells specifying specific gpio
(controller specific)
GPIO properties should be named "[<name>-]gpios", with <name> being the purpose
of this GPIO for the device. While a non-existent <name> is considered valid
for compatibility reasons (resolving to the "gpios" property), it is not allowed
for new bindings.
for new bindings. Also, GPIO properties named "[<name>-]gpio" are valid and old
bindings use it, but are only supported for compatibility reasons and should not
be used for newer bindings since it has been deprecated.
GPIO properties can contain one or more GPIO phandles, but only in exceptional
cases should they contain more than one. If your device uses several GPIOs with
@ -31,30 +24,28 @@ The following example could be used to describe GPIO pins used as device enable
and bit-banged data signals:
gpio1: gpio1 {
gpio-controller
#gpio-cells = <2>;
};
gpio2: gpio2 {
gpio-controller
#gpio-cells = <1>;
gpio-controller;
#gpio-cells = <2>;
};
[...]
enable-gpios = <&gpio2 2>;
data-gpios = <&gpio1 12 0>,
<&gpio1 13 0>,
<&gpio1 14 0>,
<&gpio1 15 0>;
Note that gpio-specifier length is controller dependent. In the
above example, &gpio1 uses 2 cells to specify a gpio, while &gpio2
only uses one.
In the above example, &gpio1 uses 2 cells to specify a gpio. The first cell is
a local offset to the GPIO line and the second cell represent consumer flags,
such as if the consumer desire the line to be active low (inverted) or open
drain. This is the recommended practice.
gpio-specifier may encode: bank, pin position inside the bank,
whether pin is open-drain and whether pin is logically inverted.
Exact meaning of each specifier cell is controller specific, and must
be documented in the device tree binding for the device. Use the macros
defined in include/dt-bindings/gpio/gpio.h whenever possible:
The exact meaning of each specifier cell is controller specific, and must be
documented in the device tree binding for the device, but it is strongly
recommended to use the two-cell approach.
Most controllers are specifying a generic flag bitfield in the last cell, so
for these, use the macros defined in
include/dt-bindings/gpio/gpio.h whenever possible:
Example of a node using GPIOs:
@ -140,6 +131,80 @@ Every GPIO controller node must contain both an empty "gpio-controller"
property, and a #gpio-cells integer property, which indicates the number of
cells in a gpio-specifier.
Some system-on-chips (SoCs) use the concept of GPIO banks. A GPIO bank is an
instance of a hardware IP core on a silicon die, usually exposed to the
programmer as a coherent range of I/O addresses. Usually each such bank is
exposed in the device tree as an individual gpio-controller node, reflecting
the fact that the hardware was synthesized by reusing the same IP block a
few times over.
Optionally, a GPIO controller may have a "ngpios" property. This property
indicates the number of in-use slots of available slots for GPIOs. The
typical example is something like this: the hardware register is 32 bits
wide, but only 18 of the bits have a physical counterpart. The driver is
generally written so that all 32 bits can be used, but the IP block is reused
in a lot of designs, some using all 32 bits, some using 18 and some using
12. In this case, setting "ngpios = <18>;" informs the driver that only the
first 18 GPIOs, at local offset 0 .. 17, are in use.
If these GPIOs do not happen to be the first N GPIOs at offset 0...N-1, an
additional set of tuples is needed to specify which GPIOs are unusable, with
the gpio-reserved-ranges binding. This property indicates the start and size
of the GPIOs that can't be used.
Optionally, a GPIO controller may have a "gpio-line-names" property. This is
an array of strings defining the names of the GPIO lines going out of the
GPIO controller. This name should be the most meaningful producer name
for the system, such as a rail name indicating the usage. Package names
such as pin name are discouraged: such lines have opaque names (since they
are by definition generic purpose) and such names are usually not very
helpful. For example "MMC-CD", "Red LED Vdd" and "ethernet reset" are
reasonable line names as they describe what the line is used for. "GPIO0"
is not a good name to give to a GPIO line. Placeholders are discouraged:
rather use the "" (blank string) if the use of the GPIO line is undefined
in your design. The names are assigned starting from line offset 0 from
left to right from the passed array. An incomplete array (where the number
of passed named are less than ngpios) will still be used up until the last
provided valid line index.
Example:
gpio-controller@00000000 {
compatible = "foo";
reg = <0x00000000 0x1000>;
gpio-controller;
#gpio-cells = <2>;
ngpios = <18>;
gpio-reserved-ranges = <0 4>, <12 2>;
gpio-line-names = "MMC-CD", "MMC-WP", "VDD eth", "RST eth", "LED R",
"LED G", "LED B", "Col A", "Col B", "Col C", "Col D",
"Row A", "Row B", "Row C", "Row D", "NMI button",
"poweroff", "reset";
}
The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
providing automatic GPIO request and configuration as part of the
gpio-controller's driver probe function.
Each GPIO hog definition is represented as a child node of the GPIO controller.
Required properties:
- gpio-hog: A property specifying that this child node represents a GPIO hog.
- gpios: Store the GPIO information (id, flags, ...) for each GPIO to
affect. Shall contain an integer multiple of the number of cells
specified in its parent node (GPIO controller node).
Only one of the following properties scanned in the order shown below.
This means that when multiple properties are present they will be searched
in the order presented below and the first match is taken as the intended
configuration.
- input: A property specifying to set the GPIO direction as input.
- output-low A property specifying to set the GPIO direction as output with
the value low.
- output-high A property specifying to set the GPIO direction as output with
the value high.
Optional properties:
- line-name: The GPIO label name. If not present the node name is used.
Example of two SOC GPIO banks defined as gpio-controller nodes:
qe_pio_a: gpio-controller@1400 {
@ -161,46 +226,40 @@ Example of two SOC GPIO banks defined as gpio-controller nodes:
Some or all of the GPIOs provided by a GPIO controller may be routed to pins
on the package via a pin controller. This allows muxing those pins between
GPIO and other functions.
GPIO and other functions. It is a fairly common practice among silicon
engineers.
2.2) Ordinary (numerical) GPIO ranges
-------------------------------------
It is useful to represent which GPIOs correspond to which pins on which pin
controllers. The gpio-ranges property described below represents this, and
contains information structures as follows:
controllers. The gpio-ranges property described below represents this with
a discrete set of ranges mapping pins from the pin controller local number space
to pins in the GPIO controller local number space.
gpio-range-list ::= <single-gpio-range> [gpio-range-list]
single-gpio-range ::= <numeric-gpio-range> | <named-gpio-range>
numeric-gpio-range ::=
<pinctrl-phandle> <gpio-base> <pinctrl-base> <count>
named-gpio-range ::= <pinctrl-phandle> <gpio-base> '<0 0>'
pinctrl-phandle : phandle to pin controller node
gpio-base : Base GPIO ID in the GPIO controller
pinctrl-base : Base pinctrl pin ID in the pin controller
count : The number of GPIOs/pins in this range
The format is: <[pin controller phandle], [GPIO controller offset],
[pin controller offset], [number of pins]>;
The "pin controller node" mentioned above must conform to the bindings
described in ../pinctrl/pinctrl-bindings.txt.
The GPIO controller offset pertains to the GPIO controller node containing the
range definition.
In case named gpio ranges are used (ranges with both <pinctrl-base> and
<count> set to 0), the property gpio-ranges-group-names contains one string
for every single-gpio-range in gpio-ranges:
gpiorange-names-list ::= <gpiorange-name> [gpiorange-names-list]
gpiorange-name : Name of the pingroup associated to the GPIO range in
the respective pin controller.
The pin controller node referenced by the phandle must conform to the bindings
described in pinctrl/pinctrl-bindings.txt.
Elements of gpiorange-names-list corresponding to numeric ranges contain
the empty string. Elements of gpiorange-names-list corresponding to named
ranges contain the name of a pin group defined in the respective pin
controller. The number of pins/GPIOs in the range is the number of pins in
that pin group.
Each offset runs from 0 to N. It is perfectly fine to pile any number of
ranges with just one pin-to-GPIO line mapping if the ranges are concocted, but
in practice these ranges are often lumped in discrete sets.
Previous versions of this binding required all pin controller nodes that
were referenced by any gpio-ranges property to contain a property named
#gpio-range-cells with value <3>. This requirement is now deprecated.
However, that property may still exist in older device trees for
compatibility reasons, and would still be required even in new device
trees that need to be compatible with older software.
Example:
Example 1:
gpio-ranges = <&foo 0 20 10>, <&bar 10 50 20>;
This means:
- pins 20..29 on pin controller "foo" is mapped to GPIO line 0..9 and
- pins 50..69 on pin controller "bar" is mapped to GPIO line 10..29
Verbose example:
qe_pio_e: gpio-controller@1460 {
#gpio-cells = <2>;
@ -211,12 +270,33 @@ Example 1:
};
Here, a single GPIO controller has GPIOs 0..9 routed to pin controller
pinctrl1's pins 20..29, and GPIOs 10..19 routed to pin controller pinctrl2's
pins 50..59.
pinctrl1's pins 20..29, and GPIOs 10..29 routed to pin controller pinctrl2's
pins 50..69.
Example 2:
gpio_pio_i: gpio-controller@14B0 {
2.3) GPIO ranges from named pin groups
--------------------------------------
It is also possible to use pin groups for gpio ranges when pin groups are the
easiest and most convenient mapping.
Both both <pinctrl-base> and <count> must set to 0 when using named pin groups
names.
The property gpio-ranges-group-names must contain exactly one string for each
range.
Elements of gpio-ranges-group-names must contain the name of a pin group
defined in the respective pin controller. The number of pins/GPIO lines in the
range is the number of pins in that pin group. The number of pins of that
group is defined int the implementation and not in the device tree.
If numerical and named pin groups are mixed, the string corresponding to a
numerical pin range in gpio-ranges-group-names must be empty.
Example:
gpio_pio_i: gpio-controller@14b0 {
#gpio-cells = <2>;
compatible = "fsl,qe-pario-bank-e", "fsl,qe-pario-bank";
reg = <0x1480 0x18>;
@ -231,66 +311,14 @@ Example 2:
"bar";
};
Here, three GPIO ranges are defined wrt. two pin controllers. pinctrl1 GPIO
ranges are defined using pin numbers whereas the GPIO ranges wrt. pinctrl2
are named "foo" and "bar".
Here, three GPIO ranges are defined referring to two pin controllers.
3) GPIO hog definitions
-----------------------
pinctrl1 GPIO ranges are defined using pin numbers whereas the GPIO ranges
in pinctrl2 are defined using the pin groups named "foo" and "bar".
The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
providing automatic GPIO request and configuration as part of the
gpio-controller's driver probe function.
Each GPIO hog definition is represented as a child node of the GPIO controller.
Required properties:
- gpio-hog: A property specifying that this child node represents a GPIO hog.
- gpios: Store the GPIO information (id, flags) for the GPIO to
affect.
! Not yet support more than one gpio !
Only one of the following properties scanned in the order shown below.
- input: A property specifying to set the GPIO direction as input.
- output-low A property specifying to set the GPIO direction as output with
the value low.
- output-high A property specifying to set the GPIO direction as output with
the value high.
Optional properties:
- line-name: The GPIO label name. If not present the node name is used.
Example:
tca6416@20 {
compatible = "ti,tca6416";
reg = <0x20>;
#gpio-cells = <2>;
gpio-controller;
env_reset {
gpio-hog;
input;
gpios = <6 GPIO_ACTIVE_LOW>;
};
boot_rescue {
gpio-hog;
input;
line-name = "foo-bar-gpio";
gpios = <7 GPIO_ACTIVE_LOW>;
};
};
For the above Example you can than access the gpio in your boardcode
with:
struct gpio_desc *desc;
int ret;
ret = gpio_hog_lookup_name("boot_rescue", &desc);
if (ret)
return;
if (dm_gpio_get_value(desc) == 1)
printf("\nBooting into Rescue System\n");
else if (dm_gpio_get_value(desc) == 0)
printf("\nBoot normal\n");
Previous versions of this binding required all pin controller nodes that
were referenced by any gpio-ranges property to contain a property named
#gpio-range-cells with value <3>. This requirement is now deprecated.
However, that property may still exist in older device trees for
compatibility reasons, and would still be required even in new device
trees that need to be compatible with older software.