Messages in this thread | | | Date | Wed, 20 Apr 2016 16:56:50 +0200 | Subject | Re: [PATCH 8/8] gpio: stmpe: configure GPIO as output by default | From | Linus Walleij <> |
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On Tue, Apr 19, 2016 at 2:18 PM, <patrice.chotard@st.com> wrote:
> From: Patrice Chotard <patrice.chotard@st.com> > > Configures all GPIOs as output, in order to minimize power > consumption when GPIOs are unused. > > Signed-off-by: Amelie DELAUNAY <amelie.delaunay@st.com> > Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Not only do you set them all to outout but also:
> + /* To minimize power consumption, configure unused GPIOs as outputs */ > + for (i = 0; i < stmpe_gpio->chip.ngpio; i++) > + stmpe_gpio_direction_output(&stmpe_gpio->chip, i, 0);
You are driving them all low.
Now GPIO is general purpose: what if they are connected to a line with a pull-up resistor?
That is not saving power, instead consuming more than if you were setting them all to 1.
I am afraid this is wrong.
What you need is to be able to define in the DT (or similar) a set of initial values for the GPIO lines, and set them to 0 for this design.
Such bindings have been discussed but no conclusion or merged patch has emerged. Please help out in driving a standard for this!
Yours, Linus Walleij
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