| Message ID | 1461068317-28016-9-git-send-email-patrice.chotard@st.com |
|---|---|
| State | New |
| Headers | show |
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 -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/gpio/gpio-stmpe.c b/drivers/gpio/gpio-stmpe.c index 45e5b92..80c6ae6 100644 --- a/drivers/gpio/gpio-stmpe.c +++ b/drivers/gpio/gpio-stmpe.c @@ -410,7 +410,7 @@ static int stmpe_gpio_probe(struct platform_device *pdev) struct stmpe *stmpe = dev_get_drvdata(pdev->dev.parent); struct device_node *np = pdev->dev.of_node; struct stmpe_gpio *stmpe_gpio; - int ret; + int ret, i; int irq = 0; irq = platform_get_irq(pdev, 0); @@ -475,6 +475,10 @@ static int stmpe_gpio_probe(struct platform_device *pdev) NULL); } + /* 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); + platform_set_drvdata(pdev, stmpe_gpio); return 0;