linux-kernel - [PATCH] leds: leds-pca963x: workaround group blink scaling issue

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Date:   Thu, 13 Oct 2016 06:16:12 -0700
From:   Matt Ranostay <mranostay@...il.com>
To:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Cc:     Matt Ranostay <matt@...ostay.consulting>,
        Tony Lindgren <tony@...mide.com>,
        Jacek Anaszewski <j.anaszewski@...sung.com>
Subject: [PATCH] leds: leds-pca963x: workaround group blink scaling issue

PCA9632TK part seems to incorrectly blink at ~1.3x of the programmed
rate. This patchset add a nxp,period-scale devicetree property to
adjust for this misconfiguration.

Cc: Tony Lindgren <tony@...mide.com>
Cc: Jacek Anaszewski <j.anaszewski@...sung.com>
Signed-off-by: Matt Ranostay <matt@...ostay.consulting>
---
 Documentation/devicetree/bindings/leds/pca963x.txt |  3 +++
 drivers/leds/leds-pca963x.c                        | 18 +++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/leds/pca963x.txt b/Documentation/devicetree/bindings/leds/pca963x.txt
index dafbe9931c2b..dfbdb123a9bf 100644
--- a/Documentation/devicetree/bindings/leds/pca963x.txt
+++ b/Documentation/devicetree/bindings/leds/pca963x.txt
@@ -7,6 +7,9 @@ Optional properties:
 - nxp,totem-pole : use totem pole (push-pull) instead of open-drain (pca9632 defaults
   to open-drain, newer chips to totem pole)
 - nxp,hw-blink : use hardware blinking instead of software blinking
+- nxp,period-scale : In some configurations, the chip blinks faster than expected.
+		     This parameter provides a scaling ratio (fixed point, decimal divided
+		     by 1000) to compensate, e.g. 1300=1.3x and 750=0.75x.
 
 Each led is represented as a sub-node of the nxp,pca963x device.
 
diff --git a/drivers/leds/leds-pca963x.c b/drivers/leds/leds-pca963x.c
index 407eba11e187..b6ce1f2ec33e 100644
--- a/drivers/leds/leds-pca963x.c
+++ b/drivers/leds/leds-pca963x.c
@@ -59,6 +59,7 @@ struct pca963x_chipdef {
 	u8			grpfreq;
 	u8			ledout_base;
 	int			n_leds;
+	unsigned int		scaling;
 };
 
 static struct pca963x_chipdef pca963x_chipdefs[] = {
@@ -189,6 +190,14 @@ static int pca963x_led_set(struct led_classdev *led_cdev,
 	return pca963x_brightness(pca963x, value);
 }
 
+static unsigned int pca963x_period_scale(struct pca963x_led *pca963x,
+	unsigned int val)
+{
+	unsigned int scaling = pca963x->chip->chipdef->scaling;
+
+	return scaling ? DIV_ROUND_CLOSEST(val * scaling, 1000) : val;
+}
+
 static int pca963x_blink_set(struct led_classdev *led_cdev,
 		unsigned long *delay_on, unsigned long *delay_off)
 {
@@ -207,14 +216,14 @@ static int pca963x_blink_set(struct led_classdev *led_cdev,
 		time_off = 500;
 	}
 
-	period = time_on + time_off;
+	period = pca963x_period_scale(pca963x, time_on + time_off);
 
 	/* If period not supported by hardware, default to someting sane. */
 	if ((period < PCA963X_BLINK_PERIOD_MIN) ||
 	    (period > PCA963X_BLINK_PERIOD_MAX)) {
 		time_on = 500;
 		time_off = 500;
-		period = time_on + time_off;
+		period = pca963x_period_scale(pca963x, 1000);
 	}
 
 	/*
@@ -222,7 +231,7 @@ static int pca963x_blink_set(struct led_classdev *led_cdev,
 	 *	(time_on / period) = (GDC / 256) ->
 	 *		GDC = ((time_on * 256) / period)
 	 */
-	gdc = (time_on * 256) / period;
+	gdc = (pca963x_period_scale(pca963x, time_on) * 256) / period;
 
 	/*
 	 * From manual: period = ((GFRQ + 1) / 24) in seconds.
@@ -294,6 +303,9 @@ pca963x_dt_init(struct i2c_client *client, struct pca963x_chipdef *chip)
 	else
 		pdata->blink_type = PCA963X_SW_BLINK;
 
+	if (of_property_read_u32(np, "nxp,period-scale", &chip->scaling))
+		chip->scaling = 1000;
+
 	return pdata;
 }
 
-- 
2.7.4