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Subject[PATCH 5/5] leds: pca955x: Implement the default-state property
Date
In order to retain the LED state after a system reboot, check the
documented default-state device tree property during initialization.
Modify the behavior of the probe according to the property.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
drivers/leds/leds-pca955x.c | 54 +++++++++++++++++++++++++++++++------
1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index e47ba7c3b7c7..fa1d77d86ef6 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -129,6 +129,7 @@ struct pca955x_led {
int led_num; /* 0 .. 15 potentially */
char name[32];
u32 type;
+ int default_state;
const char *default_trigger;
};

@@ -439,6 +440,7 @@ pca955x_get_pdata(struct i2c_client *client, struct pca955x_chipdef *chip)

device_for_each_child_node(&client->dev, child) {
const char *name;
+ const char *state;
u32 reg;
int res;

@@ -457,6 +459,18 @@ pca955x_get_pdata(struct i2c_client *client, struct pca955x_chipdef *chip)
fwnode_property_read_u32(child, "type", &led->type);
fwnode_property_read_string(child, "linux,default-trigger",
&led->default_trigger);
+
+ if (!fwnode_property_read_string(child, "default-state",
+ &state)) {
+ if (!strcmp(state, "keep"))
+ led->default_state = LEDS_GPIO_DEFSTATE_KEEP;
+ else if (!strcmp(state, "on"))
+ led->default_state = LEDS_GPIO_DEFSTATE_ON;
+ else
+ led->default_state = LEDS_GPIO_DEFSTATE_OFF;
+ } else {
+ led->default_state = LEDS_GPIO_DEFSTATE_OFF;
+ }
}

pdata->num_leds = chip->bits;
@@ -485,6 +499,7 @@ static int pca955x_probe(struct i2c_client *client,
int i, err;
struct pca955x_platform_data *pdata;
int ngpios = 0;
+ bool keep_pwm = false;

chip = &pca955x_chipdefs[id->driver_data];
adapter = client->adapter;
@@ -565,14 +580,35 @@ static int pca955x_probe(struct i2c_client *client,
led->brightness_set_blocking = pca955x_led_set;
led->brightness_get = pca955x_led_get;

+ if (pdata->leds[i].default_state ==
+ LEDS_GPIO_DEFSTATE_OFF) {
+ err = pca955x_led_set(led, LED_OFF);
+ if (err)
+ return err;
+ } else if (pdata->leds[i].default_state ==
+ LEDS_GPIO_DEFSTATE_ON) {
+ err = pca955x_led_set(led, LED_FULL);
+ if (err)
+ return err;
+ }
+
err = devm_led_classdev_register(&client->dev, led);
if (err)
return err;

- /* Turn off LED */
- err = pca955x_led_set(led, LED_OFF);
- if (err)
- return err;
+ /*
+ * For default-state == "keep", let the core update the
+ * brightness from the hardware, then check the
+ * brightness to see if it's using PWM1. If so, PWM1
+ * should not be written below.
+ */
+ if (pdata->leds[i].default_state ==
+ LEDS_GPIO_DEFSTATE_KEEP) {
+ if (led->brightness != LED_FULL &&
+ led->brightness != LED_OFF &&
+ led->brightness != LED_HALF)
+ keep_pwm = true;
+ }
}
}

@@ -581,10 +617,12 @@ static int pca955x_probe(struct i2c_client *client,
if (err)
return err;

- /* PWM1 is used for variable brightness, default to OFF */
- err = pca955x_write_pwm(client, 1, 0);
- if (err)
- return err;
+ if (!keep_pwm) {
+ /* 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);
--
2.27.0
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