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Commit 336cdba0 authored by Linus Walleij's avatar Linus Walleij
Browse files

pinctrl: documentation update 



Update the docs removing an obsolete __refdata tag and document
the mysterious return value of pin_free(). And fixes up some various
confusions in the pinctrl documentation.

Reported-by: default avatarRajendra Nayak <rnayak@ti.com>
Reported-by: default avatarRandy Dunlap <rdunlap@xenotime.net>
Reported-by: default avatarThomas Abraham <thomas.abraham@linaro.org>
Reported-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: default avatarStephen Warren <swarren@nvidia.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 3712a3c4

Documentation/pinctrl.txt

+26 −26
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ Definition of PIN: 
  be sparse - i.e. there may be gaps in the space with numbers where no

  pin exists.



When a PIN CONTROLLER is instatiated, it will register a descriptor to the

When a PIN CONTROLLER is instantiated, it will register a descriptor to the

pin control framework, and this descriptor contains an array of pin descriptors

describing the pins handled by this specific pin controller.
@@ -61,14 +61,14 @@ this in our driver: 


#include <linux/pinctrl/pinctrl.h>



const struct pinctrl_pin_desc __refdata foo_pins[] = {

      PINCTRL_PIN(0, "A1"),

      PINCTRL_PIN(1, "A2"),

      PINCTRL_PIN(2, "A3"),

const struct pinctrl_pin_desc foo_pins[] = {

      PINCTRL_PIN(0, "A8"),

      PINCTRL_PIN(1, "B8"),

      PINCTRL_PIN(2, "C8"),

      ...

      PINCTRL_PIN(61, "H6"),

      PINCTRL_PIN(62, "H7"),

      PINCTRL_PIN(63, "H8"),

      PINCTRL_PIN(61, "F1"),

      PINCTRL_PIN(62, "G1"),

      PINCTRL_PIN(63, "H1"),

};



static struct pinctrl_desc foo_desc = {
@@ -91,8 +91,8 @@ int __init foo_probe(void) 
Pins usually have fancier names than this. You can find these in the dataheet

for your chip. Notice that the core pinctrl.h file provides a fancy macro

called PINCTRL_PIN() to create the struct entries. As you can see I enumerated

the pins from 0 in the upper left corner to 63 in the lower right corner,

this enumeration was arbitrarily chosen, in practice you need to think

the pins from 0 in the upper left corner to 63 in the lower right corner.

This enumeration was arbitrarily chosen, in practice you need to think

through your numbering system so that it matches the layout of registers

and such things in your driver, or the code may become complicated. You must

also consider matching of offsets to the GPIO ranges that may be handled by
@@ -133,8 +133,8 @@ struct foo_group { 
	const unsigned num_pins;

};



static unsigned int spi0_pins[] = { 0, 8, 16, 24 };

static unsigned int i2c0_pins[] = { 24, 25 };

static const unsigned int spi0_pins[] = { 0, 8, 16, 24 };

static const unsigned int i2c0_pins[] = { 24, 25 };



static const struct foo_group foo_groups[] = {

	{
@@ -242,7 +242,7 @@ chip a: [32 .. 47] 
chip b: [48 .. 55]



When GPIO-specific functions in the pin control subsystem are called, these

ranges will be used to look up the apropriate pin controller by inspecting

ranges will be used to look up the appropriate pin controller by inspecting

and matching the pin to the pin ranges across all controllers. When a

pin controller handling the matching range is found, GPIO-specific functions

will be called on that specific pin controller.
@@ -438,7 +438,7 @@ you. Define enumerators only for the pins you can control if that makes sense. 


Assumptions:



We assume that the number possible function maps to pin groups is limited by

We assume that the number of possible function maps to pin groups is limited by

the hardware. I.e. we assume that there is no system where any function can be

mapped to any pin, like in a phone exchange. So the available pins groups for

a certain function will be limited to a few choices (say up to eight or so),
@@ -585,7 +585,7 @@ int foo_list_funcs(struct pinctrl_dev *pctldev, unsigned selector) 


const char *foo_get_fname(struct pinctrl_dev *pctldev, unsigned selector)

{

	return myfuncs[selector].name;

	return foo_functions[selector].name;

}



static int foo_get_groups(struct pinctrl_dev *pctldev, unsigned selector,
@@ -600,16 +600,16 @@ static int foo_get_groups(struct pinctrl_dev *pctldev, unsigned selector, 
int foo_enable(struct pinctrl_dev *pctldev, unsigned selector,

		unsigned group)

{

	u8 regbit = (1 << group);

	u8 regbit = (1 << selector + group);



	writeb((readb(MUX)|regbit), MUX)

	return 0;

}



int foo_disable(struct pinctrl_dev *pctldev, unsigned selector,

void foo_disable(struct pinctrl_dev *pctldev, unsigned selector,

		unsigned group)

{

	u8 regbit = (1 << group);

	u8 regbit = (1 << selector + group);



	writeb((readb(MUX) & ~(regbit)), MUX)

	return 0;
@@ -683,7 +683,7 @@ spi on the second function mapping: 


#include <linux/pinctrl/machine.h>



static struct pinmux_map pmx_mapping[] = {

static const struct pinmux_map pmx_mapping[] = {

	{

		.ctrl_dev_name = "pinctrl.0",

		.function = "spi0",
@@ -714,7 +714,7 @@ for example if they are not yet instantiated or cumbersome to obtain. 


You register this pinmux mapping to the pinmux subsystem by simply:



       ret = pinmux_register_mappings(&pmx_mapping, ARRAY_SIZE(pmx_mapping));

       ret = pinmux_register_mappings(pmx_mapping, ARRAY_SIZE(pmx_mapping));



Since the above construct is pretty common there is a helper macro to make

it even more compact which assumes you want to use pinctrl.0 and position
@@ -762,42 +762,42 @@ case), we define a mapping like this: 
	.name "2bit"

	.ctrl_dev_name = "pinctrl.0",

	.function = "mmc0",

	.group = "mmc0_0_grp",

	.group = "mmc0_1_grp",

	.dev_name = "foo-mmc.0",

},

{

	.name "4bit"

	.ctrl_dev_name = "pinctrl.0",

	.function = "mmc0",

	.group = "mmc0_0_grp",

	.group = "mmc0_1_grp",

	.dev_name = "foo-mmc.0",

},

{

	.name "4bit"

	.ctrl_dev_name = "pinctrl.0",

	.function = "mmc0",

	.group = "mmc0_1_grp",

	.group = "mmc0_2_grp",

	.dev_name = "foo-mmc.0",

},

{

	.name "8bit"

	.ctrl_dev_name = "pinctrl.0",

	.function = "mmc0",

	.group = "mmc0_0_grp",

	.group = "mmc0_1_grp",

	.dev_name = "foo-mmc.0",

},

{

	.name "8bit"

	.ctrl_dev_name = "pinctrl.0",

	.function = "mmc0",

	.group = "mmc0_1_grp",

	.group = "mmc0_2_grp",

	.dev_name = "foo-mmc.0",

},

{

	.name "8bit"

	.ctrl_dev_name = "pinctrl.0",

	.function = "mmc0",

	.group = "mmc0_2_grp",

	.group = "mmc0_3_grp",

	.dev_name = "foo-mmc.0",

},

...

drivers/pinctrl/pinmux.c

+5 −1
Original line number Diff line number Diff line
@@ -174,6 +174,10 @@ out: 
 * @pin: the pin to free

 * @gpio_range: the range matching the GPIO pin if this is a request for a

 *	single GPIO pin

 *

 * This function returns a pointer to the function name in use. This is used

 * for callers that dynamically allocate a function name so it can be freed

 * once the pin is free. This is done for GPIO request functions.

 */

static const char *pin_free(struct pinctrl_dev *pctldev, int pin,

			    struct pinctrl_gpio_range *gpio_range)
@@ -919,7 +923,7 @@ int pinmux_hog_maps(struct pinctrl_dev *pctldev) 
}



/**

 * pinmux_hog_maps() - unhog specific map entries on controller device

 * pinmux_unhog_maps() - unhog specific map entries on controller device

 * @pctldev: the pin control device to unhog entries on

 */

void pinmux_unhog_maps(struct pinctrl_dev *pctldev)