Linux-LEDs Archive on lore.kernel.org
 help / color / Atom feed
From: "Guido Günther" <agx@sigxcpu.org>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>,
	Pavel Machek <pavel@ucw.cz>, Dan Murphy <dmurphy@ti.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-leds@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v3 6/9] leds: lm3692x: Make sure we don't exceed the maximum led current
Date: Sat,  4 Jan 2020 11:54:22 +0100
Message-ID: <5826b77d42521595e93d01d53475a8881cad1875.1578134779.git.agx@sigxcpu.org> (raw)
In-Reply-To: <cover.1578134779.git.agx@sigxcpu.org>

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>
---
 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..2e24316566f5 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;
 	}
 
+	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


  parent reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-04 10:54 [PATCH v3 0/9] leds: lm3692x: Allow to set ovp and brigthness mode Guido Günther
2020-01-04 10:54 ` [PATCH v3 1/9] dt: bindings: lm3692x: Add ti,ovp-microvolt property Guido Günther
2020-01-04 21:11   ` Rob Herring
2020-01-04 10:54 ` [PATCH v3 2/9] leds: lm3692x: Allow to configure over voltage protection Guido Günther
2020-01-04 10:54 ` [PATCH v3 3/9] dt: bindings: lm3692x: Add ti,brightness-mapping-exponential property Guido Günther
2020-01-04 21:11   ` Rob Herring
2020-01-04 10:54 ` [PATCH v3 4/9] leds: lm3692x: Allow to configure brigthness mode Guido Günther
2020-01-04 10:54 ` [PATCH v3 5/9] dt: bindings: lm3692x: Add led-max-microamp property Guido Günther
2020-01-04 21:11   ` Rob Herring
2020-01-04 10:54 ` Guido Günther [this message]
2020-01-04 10:54 ` [PATCH v3 7/9] leds: lm3692x: Move lm3692x_init and rename to lm3692x_leds_enable Guido Günther
2020-01-04 10:54 ` [PATCH v3 8/9] leds: lm3692x: Split out lm3692x_leds_disable Guido Günther
2020-01-04 10:54 ` [PATCH v3 9/9] leds: lm3692x: Disable chip on brightness 0 Guido Günther
2020-01-05 23:47 ` [PATCH v3 0/9] leds: lm3692x: Allow to set ovp and brigthness mode Pavel Machek
2020-01-06  9:44   ` Guido Günther

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=5826b77d42521595e93d01d53475a8881cad1875.1578134779.git.agx@sigxcpu.org \
    --to=agx@sigxcpu.org \
    --cc=devicetree@vger.kernel.org \
    --cc=dmurphy@ti.com \
    --cc=jacek.anaszewski@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-leds@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=pavel@ucw.cz \
    --cc=robh+dt@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-LEDs Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-leds/0 linux-leds/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-leds linux-leds/ https://lore.kernel.org/linux-leds \
		linux-leds@vger.kernel.org
	public-inbox-index linux-leds

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-leds


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git