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linux/drivers/leds/leds-pca955x.c
Andrew Jeffery 52ca7d0f7b leds: pca955x: Don't invert requested value in pca955x_gpio_set_value() 
The PCA9552 lines can be used either for driving LEDs or as GPIOs. The
manual states that for LEDs, the operation is open-drain:

         The LSn LED select registers determine the source of the LED data.

           00 = output is set LOW (LED on)
           01 = output is set high-impedance (LED off; default)
           10 = output blinks at PWM0 rate
           11 = output blinks at PWM1 rate

For GPIOs it suggests a pull-up so that the open-case drives the line
high:

         For use as output, connect external pull-up resistor to the pin
         and size it according to the DC recommended operating
         characteristics.  LED output pin is HIGH when the output is
         programmed as high-impedance, and LOW when the output is
         programmed LOW through the ‘LED selector’ register.  The output
         can be pulse-width controlled when PWM0 or PWM1 are used.

Now, I have a hardware design that uses the LED controller to control
LEDs. However, for $reasons, we're using the leds-gpio driver to drive
the them. The reasons are here are a tangent but lead to the discovery
of the inversion, which manifested as the LEDs being set to full
brightness at boot when we expected them to be off.

As we're driving the LEDs through leds-gpio, this means wending our way
through the gpiochip abstractions. So with that in mind we need to
describe an active-low GPIO configuration to drive the LEDs as though
they were GPIOs.

The set() gpiochip callback in leds-pca955x does the following:

         ...
         if (val)
                pca955x_led_set(&led->led_cdev, LED_FULL);
         else
                pca955x_led_set(&led->led_cdev, LED_OFF);
         ...

Where LED_FULL = 255. pca955x_led_set() in turn does:

         ...
         switch (value) {
         case LED_FULL:
                ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_ON);
                break;
         ...

Where PCA955X_LS_LED_ON is defined as:

         #define PCA955X_LS_LED_ON	0x0	/* Output LOW */

So here we have some type confusion: We've crossed domains from GPIO
behaviour to LED behaviour without accounting for possible inversions
in the process.

Stepping back to leds-gpio for a moment, during probe() we call
create_gpio_led(), which eventually executes:

         if (template->default_state == LEDS_GPIO_DEFSTATE_KEEP) {
                state = gpiod_get_value_cansleep(led_dat->gpiod);
                if (state < 0)
                        return state;
         } else {
                state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
         }
         ...
         ret = gpiod_direction_output(led_dat->gpiod, state);

In the devicetree the GPIO is annotated as active-low, and
gpiod_get_value_cansleep() handles this for us:

         int gpiod_get_value_cansleep(const struct gpio_desc *desc)
         {
                 int value;

                 might_sleep_if(extra_checks);
                 VALIDATE_DESC(desc);
                 value = _gpiod_get_raw_value(desc);
                 if (value < 0)
                         return value;

                 if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                         value = !value;

                 return value;
         }

_gpiod_get_raw_value() in turn calls through the get() callback for the
gpiochip implementation, so returning to our get() implementation in
leds-pca955x we find we extract the raw value from hardware:

         static int pca955x_gpio_get_value(struct gpio_chip *gc, unsigned int offset)
         {
                 struct pca955x *pca955x = gpiochip_get_data(gc);
                 struct pca955x_led *led = &pca955x->leds[offset];
                 u8 reg = pca955x_read_input(pca955x->client, led->led_num / 8);

                 return !!(reg & (1 << (led->led_num % 8)));
         }

This behaviour is not symmetric with that of set(), where the val is
inverted by the driver.

Closing the loop on the GPIO_ACTIVE_LOW inversions,
gpiod_direction_output(), like gpiod_get_value_cansleep(), handles it
for us:

         int gpiod_direction_output(struct gpio_desc *desc, int value)
         {
                  VALIDATE_DESC(desc);
                  if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
                           value = !value;
                  else
                           value = !!value;
                  return _gpiod_direction_output_raw(desc, value);
         }

All-in-all, with a value of 'keep' for default-state property in a
leds-gpio child node, the current state of the hardware will in-fact be
inverted; precisely the opposite of what was intended.

Rework leds-pca955x so that we avoid the incorrect inversion and clarify
the semantics with respect to GPIO.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Tested-by: Joel Stanley <joel@jms.id.au>
Tested-by: Matt Spinler <mspinler@linux.vnet.ibm.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
2017-10-06 21:31:03 +02:00

616 lines
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/*
* Copyright 2007-2008 Extreme Engineering Solutions, Inc.
*
* Author: Nate Case <ncase@xes-inc.com>
*
* This file is subject to the terms and conditions of version 2 of
* the GNU General Public License. See the file COPYING in the main
* directory of this archive for more details.
*
* LED driver for various PCA955x I2C LED drivers
*
* Supported devices:
*
* Device Description 7-bit slave address
* ------ ----------- -------------------
* PCA9550 2-bit driver 0x60 .. 0x61
* PCA9551 8-bit driver 0x60 .. 0x67
* PCA9552 16-bit driver 0x60 .. 0x67
* PCA9553/01 4-bit driver 0x62
* PCA9553/02 4-bit driver 0x63
*
* Philips PCA955x LED driver chips follow a register map as shown below:
*
* Control Register Description
* ---------------- -----------
* 0x0 Input register 0
* ..
* NUM_INPUT_REGS - 1 Last Input register X
*
* NUM_INPUT_REGS Frequency prescaler 0
* NUM_INPUT_REGS + 1 PWM register 0
* NUM_INPUT_REGS + 2 Frequency prescaler 1
* NUM_INPUT_REGS + 3 PWM register 1
*
* NUM_INPUT_REGS + 4 LED selector 0
* NUM_INPUT_REGS + 4
* + NUM_LED_REGS - 1 Last LED selector
*
* where NUM_INPUT_REGS and NUM_LED_REGS vary depending on how many
* bits the chip supports.
*/
#include <linux/acpi.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/gpio.h>
#include <linux/i2c.h>
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <dt-bindings/leds/leds-pca955x.h>
/* LED select registers determine the source that drives LED outputs */
#define PCA955X_LS_LED_ON 0x0 /* Output LOW */
#define PCA955X_LS_LED_OFF 0x1 /* Output HI-Z */
#define PCA955X_LS_BLINK0 0x2 /* Blink at PWM0 rate */
#define PCA955X_LS_BLINK1 0x3 /* Blink at PWM1 rate */
#define PCA955X_GPIO_INPUT LED_OFF
#define PCA955X_GPIO_HIGH LED_OFF
#define PCA955X_GPIO_LOW LED_FULL
enum pca955x_type {
pca9550,
pca9551,
pca9552,
pca9553,
};
struct pca955x_chipdef {
int bits;
u8 slv_addr; /* 7-bit slave address mask */
int slv_addr_shift; /* Number of bits to ignore */
};
static struct pca955x_chipdef pca955x_chipdefs[] = {
[pca9550] = {
.bits = 2,
.slv_addr = /* 110000x */ 0x60,
.slv_addr_shift = 1,
},
[pca9551] = {
.bits = 8,
.slv_addr = /* 1100xxx */ 0x60,
.slv_addr_shift = 3,
},
[pca9552] = {
.bits = 16,
.slv_addr = /* 1100xxx */ 0x60,
.slv_addr_shift = 3,
},
[pca9553] = {
.bits = 4,
.slv_addr = /* 110001x */ 0x62,
.slv_addr_shift = 1,
},
};
static const struct i2c_device_id pca955x_id[] = {
{ "pca9550", pca9550 },
{ "pca9551", pca9551 },
{ "pca9552", pca9552 },
{ "pca9553", pca9553 },
{ }
};
MODULE_DEVICE_TABLE(i2c, pca955x_id);
static const struct acpi_device_id pca955x_acpi_ids[] = {
{ "PCA9550", pca9550 },
{ "PCA9551", pca9551 },
{ "PCA9552", pca9552 },
{ "PCA9553", pca9553 },
{ }
};
MODULE_DEVICE_TABLE(acpi, pca955x_acpi_ids);
struct pca955x {
struct mutex lock;
struct pca955x_led *leds;
struct pca955x_chipdef *chipdef;
struct i2c_client *client;
#ifdef CONFIG_LEDS_PCA955X_GPIO
struct gpio_chip gpio;
#endif
};
struct pca955x_led {
struct pca955x *pca955x;
struct led_classdev led_cdev;
int led_num; /* 0 .. 15 potentially */
char name[32];
u32 type;
const char *default_trigger;
};
struct pca955x_platform_data {
struct pca955x_led *leds;
int num_leds;
};
/* 8 bits per input register */
static inline int pca95xx_num_input_regs(int bits)
{
return (bits + 7) / 8;
}
/* 4 bits per LED selector register */
static inline int pca95xx_num_led_regs(int bits)
{
return (bits + 3) / 4;
}
/*
* Return an LED selector register value based on an existing one, with
* the appropriate 2-bit state value set for the given LED number (0-3).
*/
static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
{
return (oldval & (~(0x3 << (led_num << 1)))) |
((state & 0x3) << (led_num << 1));
}
/*
* Write to frequency prescaler register, used to program the
* period of the PWM output. period = (PSCx + 1) / 38
*/
static int pca955x_write_psc(struct i2c_client *client, int n, u8 val)
{
struct pca955x *pca955x = i2c_get_clientdata(client);
int ret;
ret = i2c_smbus_write_byte_data(client,
pca95xx_num_input_regs(pca955x->chipdef->bits) + 2*n,
val);
if (ret < 0)
dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
__func__, n, val, ret);
return ret;
}
/*
* Write to PWM register, which determines the duty cycle of the
* output. LED is OFF when the count is less than the value of this
* register, and ON when it is greater. If PWMx == 0, LED is always OFF.
*
* Duty cycle is (256 - PWMx) / 256
*/
static int pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
{
struct pca955x *pca955x = i2c_get_clientdata(client);
int ret;
ret = i2c_smbus_write_byte_data(client,
pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + 2*n,
val);
if (ret < 0)
dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
__func__, n, val, ret);
return ret;
}
/*
* Write to LED selector register, which determines the source that
* drives the LED output.
*/
static int pca955x_write_ls(struct i2c_client *client, int n, u8 val)
{
struct pca955x *pca955x = i2c_get_clientdata(client);
int ret;
ret = i2c_smbus_write_byte_data(client,
pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n,
val);
if (ret < 0)
dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
__func__, n, val, ret);
return ret;
}
/*
* Read the LED selector register, which determines the source that
* drives the LED output.
*/
static int pca955x_read_ls(struct i2c_client *client, int n, u8 *val)
{
struct pca955x *pca955x = i2c_get_clientdata(client);
int ret;
ret = i2c_smbus_read_byte_data(client,
pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n);
if (ret < 0) {
dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
__func__, n, ret);
return ret;
}
*val = (u8)ret;
return 0;
}
static int pca955x_led_set(struct led_classdev *led_cdev,
enum led_brightness value)
{
struct pca955x_led *pca955x_led;
struct pca955x *pca955x;
u8 ls;
int chip_ls; /* which LSx to use (0-3 potentially) */
int ls_led; /* which set of bits within LSx to use (0-3) */
int ret;
pca955x_led = container_of(led_cdev, struct pca955x_led, led_cdev);
pca955x = pca955x_led->pca955x;
chip_ls = pca955x_led->led_num / 4;
ls_led = pca955x_led->led_num % 4;
mutex_lock(&pca955x->lock);
ret = pca955x_read_ls(pca955x->client, chip_ls, &ls);
if (ret)
goto out;
switch (value) {
case LED_FULL:
ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_ON);
break;
case LED_OFF:
ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_OFF);
break;
case LED_HALF:
ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK0);
break;
default:
/*
* Use PWM1 for all other values. This has the unwanted
* side effect of making all LEDs on the chip share the
* same brightness level if set to a value other than
* OFF, HALF, or FULL. But, this is probably better than
* just turning off for all other values.
*/
ret = pca955x_write_pwm(pca955x->client, 1, 255 - value);
if (ret)
goto out;
ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
break;
}
ret = pca955x_write_ls(pca955x->client, chip_ls, ls);
out:
mutex_unlock(&pca955x->lock);
return ret;
}
#ifdef CONFIG_LEDS_PCA955X_GPIO
/*
* Read the INPUT register, which contains the state of LEDs.
*/
static int pca955x_read_input(struct i2c_client *client, int n, u8 *val)
{
int ret = i2c_smbus_read_byte_data(client, n);
if (ret < 0) {
dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
__func__, n, ret);
return ret;
}
*val = (u8)ret;
return 0;
}
static int pca955x_gpio_request_pin(struct gpio_chip *gc, unsigned int offset)
{
struct pca955x *pca955x = gpiochip_get_data(gc);
struct pca955x_led *led = &pca955x->leds[offset];
if (led->type == PCA955X_TYPE_GPIO)
return 0;
return -EBUSY;
}
static int pca955x_set_value(struct gpio_chip *gc, unsigned int offset,
int val)
{
struct pca955x *pca955x = gpiochip_get_data(gc);
struct pca955x_led *led = &pca955x->leds[offset];
if (val)
return pca955x_led_set(&led->led_cdev, PCA955X_GPIO_HIGH);
return pca955x_led_set(&led->led_cdev, PCA955X_GPIO_LOW);
}
static void pca955x_gpio_set_value(struct gpio_chip *gc, unsigned int offset,
int val)
{
pca955x_set_value(gc, offset, val);
}
static int pca955x_gpio_get_value(struct gpio_chip *gc, unsigned int offset)
{
struct pca955x *pca955x = gpiochip_get_data(gc);
struct pca955x_led *led = &pca955x->leds[offset];
u8 reg = 0;
/* There is nothing we can do about errors */
pca955x_read_input(pca955x->client, led->led_num / 8, &reg);
return !!(reg & (1 << (led->led_num % 8)));
}
static int pca955x_gpio_direction_input(struct gpio_chip *gc,
unsigned int offset)
{
struct pca955x *pca955x = gpiochip_get_data(gc);
struct pca955x_led *led = &pca955x->leds[offset];
/* To use as input ensure pin is not driven. */
return pca955x_led_set(&led->led_cdev, PCA955X_GPIO_INPUT);
}
static int pca955x_gpio_direction_output(struct gpio_chip *gc,
unsigned int offset, int val)
{
return pca955x_set_value(gc, offset, val);
}
#endif /* CONFIG_LEDS_PCA955X_GPIO */
#if IS_ENABLED(CONFIG_OF)
static struct pca955x_platform_data *
pca955x_pdata_of_init(struct i2c_client *client, struct pca955x_chipdef *chip)
{
struct device_node *np = client->dev.of_node;
struct device_node *child;
struct pca955x_platform_data *pdata;
int count;
count = of_get_child_count(np);
if (!count || count > chip->bits)
return ERR_PTR(-ENODEV);
pdata = devm_kzalloc(&client->dev, sizeof(*pdata), GFP_KERNEL);
if (!pdata)
return ERR_PTR(-ENOMEM);
pdata->leds = devm_kzalloc(&client->dev,
sizeof(struct pca955x_led) * chip->bits,
GFP_KERNEL);
if (!pdata->leds)
return ERR_PTR(-ENOMEM);
for_each_child_of_node(np, child) {
const char *name;
u32 reg;
int res;
res = of_property_read_u32(child, "reg", &reg);
if ((res != 0) || (reg >= chip->bits))
continue;
if (of_property_read_string(child, "label", &name))
name = child->name;
snprintf(pdata->leds[reg].name, sizeof(pdata->leds[reg].name),
"%s", name);
pdata->leds[reg].type = PCA955X_TYPE_LED;
of_property_read_u32(child, "type", &pdata->leds[reg].type);
of_property_read_string(child, "linux,default-trigger",
&pdata->leds[reg].default_trigger);
}
pdata->num_leds = chip->bits;
return pdata;
}
static const struct of_device_id of_pca955x_match[] = {
{ .compatible = "nxp,pca9550", .data = (void *)pca9550 },
{ .compatible = "nxp,pca9551", .data = (void *)pca9551 },
{ .compatible = "nxp,pca9552", .data = (void *)pca9552 },
{ .compatible = "nxp,pca9553", .data = (void *)pca9553 },
{},
};
MODULE_DEVICE_TABLE(of, of_pca955x_match);
#else
static struct pca955x_platform_data *
pca955x_pdata_of_init(struct i2c_client *client, struct pca955x_chipdef *chip)
{
return ERR_PTR(-ENODEV);
}
#endif
static int pca955x_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct pca955x *pca955x;
struct pca955x_led *pca955x_led;
struct pca955x_chipdef *chip;
struct i2c_adapter *adapter;
int i, err;
struct pca955x_platform_data *pdata;
int ngpios = 0;
if (id) {
chip = &pca955x_chipdefs[id->driver_data];
} else {
const struct acpi_device_id *acpi_id;
acpi_id = acpi_match_device(pca955x_acpi_ids, &client->dev);
if (!acpi_id)
return -ENODEV;
chip = &pca955x_chipdefs[acpi_id->driver_data];
}
adapter = to_i2c_adapter(client->dev.parent);
pdata = dev_get_platdata(&client->dev);
if (!pdata) {
pdata = pca955x_pdata_of_init(client, chip);
if (IS_ERR(pdata))
return PTR_ERR(pdata);
}
/* Make sure the slave address / chip type combo given is possible */
if ((client->addr & ~((1 << chip->slv_addr_shift) - 1)) !=
chip->slv_addr) {
dev_err(&client->dev, "invalid slave address %02x\n",
client->addr);
return -ENODEV;
}
dev_info(&client->dev, "leds-pca955x: Using %s %d-bit LED driver at "
"slave address 0x%02x\n",
client->name, chip->bits, client->addr);
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
return -EIO;
if (pdata->num_leds != chip->bits) {
dev_err(&client->dev,
"board info claims %d LEDs on a %d-bit chip\n",
pdata->num_leds, chip->bits);
return -ENODEV;
}
pca955x = devm_kzalloc(&client->dev, sizeof(*pca955x), GFP_KERNEL);
if (!pca955x)
return -ENOMEM;
pca955x->leds = devm_kzalloc(&client->dev,
sizeof(*pca955x_led) * chip->bits, GFP_KERNEL);
if (!pca955x->leds)
return -ENOMEM;
i2c_set_clientdata(client, pca955x);
mutex_init(&pca955x->lock);
pca955x->client = client;
pca955x->chipdef = chip;
for (i = 0; i < chip->bits; i++) {
pca955x_led = &pca955x->leds[i];
pca955x_led->led_num = i;
pca955x_led->pca955x = pca955x;
pca955x_led->type = pdata->leds[i].type;
switch (pca955x_led->type) {
case PCA955X_TYPE_NONE:
break;
case PCA955X_TYPE_GPIO:
ngpios++;
break;
case PCA955X_TYPE_LED:
/*
* Platform data can specify LED names and
* default triggers
*/
if (pdata->leds[i].name[0] == '\0')
snprintf(pdata->leds[i].name,
sizeof(pdata->leds[i].name), "%d", i);
snprintf(pca955x_led->name,
sizeof(pca955x_led->name), "pca955x:%s",
pdata->leds[i].name);
if (pdata->leds[i].default_trigger)
pca955x_led->led_cdev.default_trigger =
pdata->leds[i].default_trigger;
pca955x_led->led_cdev.name = pca955x_led->name;
pca955x_led->led_cdev.brightness_set_blocking =
pca955x_led_set;
err = devm_led_classdev_register(&client->dev,
&pca955x_led->led_cdev);
if (err)
return err;
/* Turn off LED */
err = pca955x_led_set(&pca955x_led->led_cdev, LED_OFF);
if (err)
return err;
}
}
/* PWM0 is used for half brightness or 50% duty cycle */
err = pca955x_write_pwm(client, 0, 255 - LED_HALF);
if (err)
return err;
/* PWM1 is used for variable brightness, default to OFF */
err = pca955x_write_pwm(client, 1, 0);
if (err)
return err;
/* Set to fast frequency so we do not see flashing */
err = pca955x_write_psc(client, 0, 0);
if (err)
return err;
err = pca955x_write_psc(client, 1, 0);
if (err)
return err;
#ifdef CONFIG_LEDS_PCA955X_GPIO
if (ngpios) {
pca955x->gpio.label = "gpio-pca955x";
pca955x->gpio.direction_input = pca955x_gpio_direction_input;
pca955x->gpio.direction_output = pca955x_gpio_direction_output;
pca955x->gpio.set = pca955x_gpio_set_value;
pca955x->gpio.get = pca955x_gpio_get_value;
pca955x->gpio.request = pca955x_gpio_request_pin;
pca955x->gpio.can_sleep = 1;
pca955x->gpio.base = -1;
pca955x->gpio.ngpio = ngpios;
pca955x->gpio.parent = &client->dev;
pca955x->gpio.owner = THIS_MODULE;
err = devm_gpiochip_add_data(&client->dev, &pca955x->gpio,
pca955x);
if (err) {
/* Use data->gpio.dev as a flag for freeing gpiochip */
pca955x->gpio.parent = NULL;
dev_warn(&client->dev, "could not add gpiochip\n");
return err;
}
dev_info(&client->dev, "gpios %i...%i\n",
pca955x->gpio.base, pca955x->gpio.base +
pca955x->gpio.ngpio - 1);
}
#endif
return 0;
}
static struct i2c_driver pca955x_driver = {
.driver = {
.name = "leds-pca955x",
.acpi_match_table = ACPI_PTR(pca955x_acpi_ids),
.of_match_table = of_match_ptr(of_pca955x_match),
},
.probe = pca955x_probe,
.id_table = pca955x_id,
};
module_i2c_driver(pca955x_driver);
MODULE_AUTHOR("Nate Case <ncase@xes-inc.com>");
MODULE_DESCRIPTION("PCA955x LED driver");
MODULE_LICENSE("GPL v2");
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