The LP8556 datasheet describes an EN/VDDIO input, which serves "both as
a chip enable and as a power supply reference for PWM, SDA, and SCL
inputs." The LP8556 that I'm testing doesn't respond properly if I try
to talk I2C to it too quickly after enabling VDDIO, and the LP8555
datasheet mentions a t_RESPONSE delay of up to 1 millisecond.
Support this EN/VDDIO by adding a regulator property to the binding;
enabling this regulator at probe time; and sleeping for 1 to 2ms, if the
EN/VDDIO regulator was provided.
Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
---
.../devicetree/bindings/leds/backlight/lp855x.txt | 2 ++
drivers/video/backlight/lp855x_bl.c | 29 ++++++++++++++++++++++
2 files changed, 31 insertions(+)
diff --git a/Documentation/devicetree/bindings/leds/backlight/lp855x.txt b/Documentation/devicetree/bindings/leds/backlight/lp855x.txt
index 0a3ecbc3a1b9..88f56641fc28 100644
--- a/Documentation/devicetree/bindings/leds/backlight/lp855x.txt
+++ b/Documentation/devicetree/bindings/leds/backlight/lp855x.txt
@@ -13,6 +13,7 @@ Optional properties:
- rom-addr: Register address of ROM area to be updated (u8)
- rom-val: Register value to be updated (u8)
- power-supply: Regulator which controls the 3V rail
+ - enable-supply: Regulator which controls the EN/VDDIO input
Example:
@@ -57,6 +58,7 @@ Example:
backlight@2c {
compatible = "ti,lp8557";
reg = <0x2c>;
+ enable-supply = <&backlight_vddio>;
power-supply = <&backlight_vdd>;
dev-ctrl = /bits/ 8 <0x41>;
diff --git a/drivers/video/backlight/lp855x_bl.c b/drivers/video/backlight/lp855x_bl.c
index e5b14f52628f..7e1f9a78674e 100644
--- a/drivers/video/backlight/lp855x_bl.c
+++ b/drivers/video/backlight/lp855x_bl.c
@@ -13,6 +13,7 @@
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/backlight.h>
+#include <linux/delay.h>
#include <linux/err.h>
#include <linux/of.h>
#include <linux/platform_data/lp855x.h>
@@ -74,6 +75,7 @@ struct lp855x {
struct lp855x_platform_data *pdata;
struct pwm_device *pwm;
struct regulator *supply; /* regulator for VDD input */
+ struct regulator *enable; /* regulator for EN/VDDIO input */
};
static int lp855x_write_byte(struct lp855x *lp, u8 reg, u8 data)
@@ -433,6 +435,19 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
lp->supply = NULL;
}
+ lp->enable = devm_regulator_get_optional(lp->dev, "enable");
+ if (IS_ERR(lp->enable)) {
+ ret = PTR_ERR(lp->enable);
+ if (ret == -ENODEV) {
+ lp->enable = NULL;
+ } else {
+ if (ret != -EPROBE_DEFER)
+ dev_err(lp->dev, "error getting enable regulator: %d\n",
+ ret);
+ return ret;
+ }
+ }
+
if (lp->supply) {
ret = regulator_enable(lp->supply);
if (ret < 0) {
@@ -441,6 +456,20 @@ static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
}
}
+ if (lp->enable) {
+ ret = regulator_enable(lp->enable);
+ if (ret < 0) {
+ dev_err(lp->dev, "failed to enable vddio: %d\n", ret);
+ return ret;
+ }
+
+ /*
+ * TS8555 datasheet says t_RESPONSE (time between VDDIO and
+ * I2C) is 1ms.
+ */
+ usleep_range(1000, 2000);
+ }
+
i2c_set_clientdata(cl, lp);
ret = lp855x_configure(lp);
--
2.8.0.rc3.226.g39d4020
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