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 formular for the lm36923 is identical according to the data sheet. Signed-off-by: Guido Günther <agx@xxxxxxxxxxx> --- drivers/leds/leds-lm3692x.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/drivers/leds/leds-lm3692x.c b/drivers/leds/leds-lm3692x.c index ff20560a8263..d7e5de8fe8db 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> @@ -320,11 +321,29 @@ static int lm3692x_init(struct lm3692x_led *led) 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 */ + if (led->brightness_ctrl & LM3692X_MAP_MODE_EXP) { + /* 228 =~ 1.0 / log2(1.003040572) */ + max_code = ilog2(max_cur/50) * 228; + } else { + 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; bool exp_mode; int ret; @@ -397,6 +416,10 @@ static int lm3692x_probe_dt(struct lm3692x_led *led) return 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 = ":"; -- 2.23.0
