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authorGuido Günther <agx@sigxcpu.org>2020-01-06 16:48:50 +0100
committerPavel <pavel@ucw.cz>2020-01-07 14:08:38 +0100
commitdf7083b57331da0222380392d8d0d8b39972bef9 (patch)
treea3bcd00e666d143379ea065ea73000f9f68d1f46 /drivers
parentdt: bindings: lm3692x: Add led-max-microamp property (diff)
downloadlinux-dev-df7083b57331da0222380392d8d0d8b39972bef9.tar.xz
linux-dev-df7083b57331da0222380392d8d0d8b39972bef9.zip
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.c20
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 = ":";