linux-kernel - Re: [PATCH v2] backlight: lp855x: Add enable regulator

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Message-ID: <20160615083445.GA1579@dell>
Date:	Wed, 15 Jun 2016 09:34:45 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Brian Norris <briannorris@...omium.org>
Cc:	Milo Kim <milo.kim@...com>, Jingoo Han <jingoohan1@...il.com>,
	Stephen Barber <smbarber@...omium.org>,
	Doug Anderson <dianders@...omium.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-fbdev@...r.kernel.org
Subject: Re: [PATCH v2] backlight: lp855x: Add enable regulator

On Fri, 10 Jun 2016, Brian Norris wrote:

> 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@...omium.org>
> ---
> v2: s/TS8555/LP8555/ in comment (typo)
> 
>  .../devicetree/bindings/leds/backlight/lp855x.txt  |  2 ++
>  drivers/video/backlight/lp855x_bl.c                | 29 ++++++++++++++++++++++
>  2 files changed, 31 insertions(+)

Collected Acks and applied, thanks.

> 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..939f057836e1 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;
> +		}
> +
> +		/*
> +		 * LP8555 datasheet says t_RESPONSE (time between VDDIO and
> +		 * I2C) is 1ms.
> +		 */
> +		usleep_range(1000, 2000);
> +	}
> +
>  	i2c_set_clientdata(cl, lp);
>  
>  	ret = lp855x_configure(lp);

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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