Hi Jeff, On Wed, Apr 19, 2023 at 8:21 AM Jeff LaBundy <jeff@xxxxxxxxxxx> wrote: > > Hi Fei, > > On Tue, Apr 18, 2023 at 08:49:51PM +0800, Fei Shao wrote: > > We observed that on Chromebook device Steelix, if Goodix GT7375P > > touchscreen is powered in suspend (because, for example, it connects to > > an always-on regulator) and with the reset GPIO asserted, it will > > introduce about 14mW power leakage. > > > > This property is used to indicate that the touchscreen is powered in > > suspend. If it's set, the driver will stop asserting the reset GPIO in > > power-down, and it will do it in power-up instead to ensure that the > > state is always reset after resuming. > > > > Signed-off-by: Fei Shao <fshao@xxxxxxxxxxxx> > > --- > > This is an interesting problem; were you able to root-cause why the silicon > exhibits this behavior? Simply asserting reset should not cause it to draw > additional power, let alone 14 mW. This almost sounds like a back-powering > problem during suspend. > There was a fix for this behavior before so I didn't dig into it on the silicon side. I can ask internally and see if we can have Goodix to confirm this is a known HW erratum. > If this is truly expected behavior, is it sufficient to use the always_on > constraint of the relevant regulator(s) to make this decision as opposed to > introducing a new property? > That sounds good to me. IIUC, for the existing designs, the boards that would set this property would also exclusively set `regulator-always-on` in their supply, so that should suffice. Let me revise the patch. Thanks! Fei > > > > Documentation/devicetree/bindings/input/goodix,gt7375p.yaml | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml > > index ce18d7dadae2..942acb286d77 100644 > > --- a/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml > > +++ b/Documentation/devicetree/bindings/input/goodix,gt7375p.yaml > > @@ -43,6 +43,12 @@ properties: > > itself as long as it allows the main board to make signals compatible > > with what the touchscreen is expecting for its IO rails. > > > > + powered-in-suspend: > > + description: > > + This indicates that the touchscreen is powered in suspend, so the driver > > + will not assert the reset GPIO in power-down to prevent power leakage. > > + type: boolean > > + > > required: > > - compatible > > - reg > > -- > > 2.40.0.634.g4ca3ef3211-goog > > > > Kind regards, > Jeff LaBundy
