diff options
| author | Guido Günther <agx@sigxcpu.org> | 2020-01-06 16:48:50 +0100 |
|---|---|---|
| committer | Pavel <pavel@ucw.cz> | 2020-01-07 14:08:38 +0100 |
| commit | df7083b57331da0222380392d8d0d8b39972bef9 (patch) | |
| tree | a3bcd00e666d143379ea065ea73000f9f68d1f46 /drivers | |
| parent | 3e0801b62a30f5c83df0b7c75afce50061401e30 (diff) | |
| download | linux-df7083b57331da0222380392d8d0d8b39972bef9.tar.bz2 | |
leds: lm3692x: Make sure we don't exceed the maximum LED current
The current is given by the formular from page 12 of
https://www.ti.com/lit/ds/symlink/lm36922.pdf. We use this to limit the
led's max_brightness using the led-max-microamp DT property.
The formula for the lm36923 is identical according to the data sheet.
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/leds/leds-lm3692x.c | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/drivers/leds/leds-lm3692x.c b/drivers/leds/leds-lm3692x.c index 28973cc5a6cc..1b056af60bd6 100644 --- a/drivers/leds/leds-lm3692x.c +++ b/drivers/leds/leds-lm3692x.c @@ -6,6 +6,7 @@ #include <linux/i2c.h> #include <linux/init.h> #include <linux/leds.h> +#include <linux/log2.h> #include <linux/module.h> #include <linux/mutex.h> #include <linux/of.h> @@ -321,11 +322,24 @@ out: return ret; } +static enum led_brightness lm3692x_max_brightness(struct lm3692x_led *led, + u32 max_cur) +{ + u32 max_code; + + /* see p.12 of LM36922 data sheet for brightness formula */ + max_code = ((max_cur * 1000) - 37806) / 12195; + if (max_code > 0x7FF) + max_code = 0x7FF; + + return max_code >> 3; +} + static int lm3692x_probe_dt(struct lm3692x_led *led) { struct fwnode_handle *child = NULL; struct led_init_data init_data = {}; - u32 ovp; + u32 ovp, max_cur; int ret; led->enable_gpio = devm_gpiod_get_optional(&led->client->dev, @@ -391,6 +405,10 @@ static int lm3692x_probe_dt(struct lm3692x_led *led) return ret; } + ret = fwnode_property_read_u32(child, "led-max-microamp", &max_cur); + led->led_dev.max_brightness = ret ? LED_FULL : + lm3692x_max_brightness(led, max_cur); + init_data.fwnode = child; init_data.devicename = led->client->name; init_data.default_label = ":"; |