On Wed, Oct 14, 2020 at 04:42:20PM -0700, Douglas Anderson wrote: > Apparently some devices connected via i2c-hid have timing requirements > around when a reset GPIO should be asserted to them. The diagram I > have seen, which I believe is from a Goodix device, looked like this: > > +---------------------------------- > | > AVDD ----+ > +------------------------------ > | (a) | > RESET ---------+ > +------------- > | (b) | > I2C comm OK ---------+ > > Where (a) is 10 ms and (b) is 120 ms. > > Let's add the ability to specify these timings to the devicetree > bindings. > > Signed-off-by: Douglas Anderson <[email protected]> > --- > I notice this bindings file is still a ".txt" file. Some searching on > The Internets(TM) shows that Rob has maybe started a conversion 5 > years ago [1], but that looks ancient. I can try to put something > together if need be, or we can just land this fix. ;-)
That was attempt number 1 using YAML... > Note that the .txt version of the bindings seems to indicate that > anyone using one of the optional properties is supposed to declare > their special compatible string. I'm not sure if that's still > considered important or not? Once you manage to get these devices > powered on and talking i2c they self-describe themselves... This change is exactly why devices should have specific compatible strings. > > [1] > https://kernel.googlesource.com/pub/scm/linux/kernel/git/robh/linux/+/refs/heads/dt-yaml/Documentation/devicetree/bindings/hid/hid-over-i2c.yaml > > Documentation/devicetree/bindings/input/hid-over-i2c.txt | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/Documentation/devicetree/bindings/input/hid-over-i2c.txt > b/Documentation/devicetree/bindings/input/hid-over-i2c.txt > index c76bafaf98d2..6fca39aa8cc6 100644 > --- a/Documentation/devicetree/bindings/input/hid-over-i2c.txt > +++ b/Documentation/devicetree/bindings/input/hid-over-i2c.txt > @@ -32,6 +32,11 @@ device-specific compatible properties, which should be > used in addition to the > - vdd-supply: phandle of the regulator that provides the supply voltage. > - post-power-on-delay-ms: time required by the device after enabling its > regulators > or powering it on, before it is ready for communication. > +- reset-gpios: GPIOs to assert to reset the device. This GPIO is asserted > when > + the device is powered off and released post-power-on-delay-ms after > + enabling the regulators. > +- post-gpio-reset-delay-ms: After deasserting reset we'll delay for this many > + more milliseconds. IMO, you should imply this from the compatible string. Rob
