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 <[email protected]>
---
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
On Wed 2019-12-25 12:07:19, Guido G?nther wrote:
1;2802;0c> 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.
formula?
> 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);
> +
Umm. Should ret come from this fwnode_property_read_u32()?
With that fixed,
Acked-by: Pavel Machek <[email protected]>
(Feel free to wait for Rob before resending the series, and I guess
you can merge it with the next one).
Best regards,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Hi,
On Thu, Dec 26, 2019 at 11:13:36AM +0100, Pavel Machek wrote:
> On Wed 2019-12-25 12:07:19, Guido G?nther wrote:
> 1;2802;0c> 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.
>
> formula?
>
> > 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);
> > +
>
> Umm. Should ret come from this fwnode_property_read_u32()?
Argh...i was sure i had that fixed (and tested without setting
led-max-microamp) but it was sitting on another branch. Thanks a lot for
catching that!
-- Guido
>
> With that fixed,
>
> Acked-by: Pavel Machek <[email protected]>
>
> (Feel free to wait for Rob before resending the series, and I guess
> you can merge it with the next one).
>
> Best regards,
> Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html