From: Andreas Kemnade <andreas@kemnade.info>
To: Dan Murphy <dmurphy@ti.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>,
<lee.jones@linaro.org>, <jingoohan1@gmail.com>,
<jacek.anaszewski@gmail.com>, <pavel@ucw.cz>,
<robh+dt@kernel.org>, <mark.rutland@arm.com>,
<b.zolnierkie@samsung.com>, <dri-devel@lists.freedesktop.org>,
<linux-leds@vger.kernel.org>, <devicetree@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-fbdev@vger.kernel.org>,
"H. Nikolaus Schaller" <hns@goldelico.com>
Subject: Re: [PATCH v2 2/2] backlight: lm3630a: add an enable gpio for the HWEN pin
Date: Wed, 11 Sep 2019 22:25:13 +0200 [thread overview]
Message-ID: <20190911222513.489b5235@aktux> (raw)
In-Reply-To: <a3f10318-11f4-3b78-47e5-d9add8a46791@ti.com>
On Wed, 11 Sep 2019 13:48:36 -0500
Dan Murphy <dmurphy@ti.com> wrote:
> >> @@ -535,6 +538,13 @@ static int lm3630a_probe(struct i2c_client *client,
> >> }
> >> pchip->pdata = pdata;
> >>
> >> + pchip->enable_gpio = devm_gpiod_get_optional(&client->dev, "enable",
> >> + GPIOD_OUT_HIGH);
> >> + if (IS_ERR(pchip->enable_gpio)) {
> >> + rval = PTR_ERR(pchip->enable_gpio);
> >> + return rval;
>
> the enable gpio is optional so if it fails you log the error and move on
>
well, if the gpio is not there, then it returns NULL.
It might return e.g. -EDEFER. So I need to check for errors here.
> Also on driver removal did you want to set the GPIO to low to disable
> the device to save power?
>
page 5 of the datasheet says:
Ishdn = Typ. 1µA max. 4µA.
For HWEN=Vin, I2c shutdown (I guess this means outputs powered off)
ond for HWEN=GND.
So are we really saving something here?
Regards,
Andreas
next prev parent reply other threads:[~2019-09-11 20:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-10 21:29 [PATCH v2 0/2] backlight_lm3630a: add enable_gpios property Andreas Kemnade
2019-09-10 21:29 ` [PATCH v2 1/2] dt-bindings: backlight: lm3630a: add enable_gpios Andreas Kemnade
2019-09-11 10:08 ` Daniel Thompson
2019-09-11 18:44 ` Dan Murphy
2019-09-10 21:29 ` [PATCH v2 2/2] backlight: lm3630a: add an enable gpio for the HWEN pin Andreas Kemnade
2019-09-11 10:25 ` Daniel Thompson
2019-09-11 18:48 ` Dan Murphy
2019-09-11 20:25 ` Andreas Kemnade [this message]
2019-09-12 9:18 ` Daniel Thompson
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