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

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Date:	Fri, 10 Jun 2016 16:52:43 -0700
From:	Stephen Barber <smbarber@...omium.org>
To:	Brian Norris <briannorris@...omium.org>
Cc:	Milo Kim <milo.kim@...com>, Jingoo Han <jingoohan1@...il.com>,
	Lee Jones <lee.jones@...aro.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, Jun 10, 2016 at 12:39 PM, Brian Norris <briannorris@...omium.org> 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(+)
>
> 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);
> --
> 2.8.0.rc3.226.g39d4020
>

Reviewed-by: Stephen Barber <smbarber@...omium.org>

Steve