On Tue, Feb 25, 2025 at 11:16:07AM +0100, Markus Burri wrote:
> On Mon, Feb 24, 2025 at 10:46:09PM -0800, Dmitry Torokhov wrote:
> > On Wed, Feb 19, 2025 at 05:42:00PM +0100, Manuel Traut wrote:
> > > On Fri, Jan 10, 2025 at 06:49:03AM +0100, Markus Burri wrote:
> > > > The property is implemented in the driver but not described in dt-bindings.
> > > > Add missing property 'gpio-activelow' to DT schema.
> > > >
> > > > Signed-off-by: Markus Burri <markus.burri@xxxxxx>
> > >
> > > Reviewed-by: Manuel Traut <manuel.traut@xxxxxx>
> > >
> > > > ---
> > > > .../devicetree/bindings/input/gpio-matrix-keypad.yaml | 6 ++++++
> > > > 1 file changed, 6 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml b/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml
> > > > index 0f348b9..9c91224 100644
> > > > --- a/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml
> > > > +++ b/Documentation/devicetree/bindings/input/gpio-matrix-keypad.yaml
> > > > @@ -40,6 +40,12 @@ properties:
> > > > type: boolean
> > > > description: Do not enable autorepeat feature.
> > > >
> > > > + gpio-activelow:
> > > > + type: boolean
> > > > + deprecated: true
> > > > + description:
> > > > + The GPIOs are low active (deprecated).
> > > > + Use the GPIO-flags in gpio controller instead of this property.
> >
> > No, we unfortunately can not rely on GPIO-flags. This is not how driver
> > works: current driver behavior is to force GPIOs as active high if the
> > property is missing and ignore polarity specified in GPIO property.
>
> So you mean this property is still valid?
> Current implementation toggle the GPIO flags to low active if the property and the GPIO flags are different.
> So in case of missing property (false) the settings from GPIO flags will be used.
> In case of gpio-activelow (true) GPIO flags are set to low active.
The driver does:
active_low = device_property_read_bool(&pdev->dev, "gpio-activelow");
...
if (active_low ^ gpiod_is_active_low(keypad->col_gpios[i]))
gpiod_toggle_active_low(keypad->col_gpios[i]);
f the property is present active_low is true. If it is absent active_low
is false. And the code below, if GPIO polarity setting from DT disagree
with active_low value it will flip GPIO polarity.
You probably think that gpiod_toggle_active_low() sets line as active
low, when in fact it flips to opposite setting:
void gpiod_toggle_active_low(struct gpio_desc *desc)
{
VALIDATE_DESC_VOID(desc);
change_bit(FLAG_ACTIVE_LOW, &desc->flags);
^^^ flip, not set or clear.
gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
}
>
> So I will remove the deprecated flag and change the description to:
> "Force GPIO flags to active low. Use GPIO flags if property is missing."
> OK?
No. It should say:
"Force GPIO polarity to active low. In the absence of this property
GPIOs are treated as active high."
Thanks.
--
Dmitry
