linux-kernel - Re: [PATCH v3 1/4] dt-bindings: input: touchscreen: goodix: Document AVDD28-supply property

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Message-ID: <20190219081510.GB65896@dtor-ws>
Date:   Tue, 19 Feb 2019 00:15:10 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Jagan Teki <jagan@...rulasolutions.com>
Cc:     Rob Herring <robh@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Chen-Yu Tsai <wens@...e.org>, linux-input@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Trimarchi <michael@...rulasolutions.com>,
        linux-amarula@...rulasolutions.com
Subject: Re: [PATCH v3 1/4] dt-bindings: input: touchscreen: goodix: Document
 AVDD28-supply property

On Tue, Feb 19, 2019 at 01:00:19AM +0530, Jagan Teki wrote:
> On Mon, Feb 18, 2019 at 3:03 PM Jagan Teki <jagan@...rulasolutions.com> wrote:
> >
> > Hi Dmitry,
> >
> > On Mon, Feb 18, 2019 at 12:42 PM Dmitry Torokhov
> > <dmitry.torokhov@...il.com> wrote:
> > >
> > > On Sun, Feb 17, 2019 at 02:45:52PM +0530, Jagan Teki wrote:
> > > > On Sun, Feb 17, 2019 at 1:21 PM Jagan Teki <jagan@...rulasolutions.com> wrote:
> > > > >
> > > > > Hi Dmitry and Rob,
> > > > >
> > > > > On Thu, Feb 14, 2019 at 3:21 AM Rob Herring <robh@...nel.org> wrote:
> > > > > >
> > > > > > On Tue, Jan 22, 2019 at 7:39 AM Jagan Teki <jagan@...rulasolutions.com> wrote:
> > > > > > >
> > > > > > > On Mon, Jan 21, 2019 at 9:46 PM Rob Herring <robh@...nel.org> wrote:
> > > > > > > >
> > > > > > > > On Fri, Jan 18, 2019 at 10:01 AM Jagan Teki <jagan@...rulasolutions.com> wrote:
> > > > > > > > >
> > > > > > > > > On Wed, Jan 9, 2019 at 7:08 PM Rob Herring <robh@...nel.org> wrote:
> > > > > > > > > >
> > > > > > > > > > Please CC DT list if you want bindings reviewed.
> > > > > > > > >
> > > > > > > > > Sorry I forgot.
> > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > On Wed, Jan 9, 2019 at 1:40 AM Dmitry Torokhov
> > > > > > > > > > <dmitry.torokhov@...il.com> wrote:
> > > > > > > > > > >
> > > > > > > > > > > On Sat, Dec 15, 2018 at 08:47:59PM +0530, Jagan Teki wrote:
> > > > > > > > > > > > Most of the Goodix CTP controllers are supply with AVDD28 pin.
> > > > > > > > > > > > which need to supply for controllers like GT5663 on some boards
> > > > > > > > > > > > to trigger the power.
> > > > > > > > > > > >
> > > > > > > > > > > > So, document the supply property so-that the require boards
> > > > > > > > > > > > that used on GT5663 can enable it via device tree.
> > > > > > > > > > > >
> > > > > > > > > > > > Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
> > > > > > > > > > > > ---
> > > > > > > > > > > >  Documentation/devicetree/bindings/input/touchscreen/goodix.txt | 1 +
> > > > > > > > > > > >  1 file changed, 1 insertion(+)
> > > > > > > > > > > >
> > > > > > > > > > > > diff --git a/Documentation/devicetree/bindings/input/touchscreen/goodix.txt b/Documentation/devicetree/bindings/input/touchscreen/goodix.txt
> > > > > > > > > > > > index f7e95c52f3c7..c4622c983e08 100644
> > > > > > > > > > > > --- a/Documentation/devicetree/bindings/input/touchscreen/goodix.txt
> > > > > > > > > > > > +++ b/Documentation/devicetree/bindings/input/touchscreen/goodix.txt
> > > > > > > > > > > > @@ -23,6 +23,7 @@ Optional properties:
> > > > > > > > > > > >   - touchscreen-inverted-y  : Y axis is inverted (boolean)
> > > > > > > > > > > >   - touchscreen-swapped-x-y : X and Y axis are swapped (boolean)
> > > > > > > > > > > >                               (swapping is done after inverting the axis)
> > > > > > > > > > > > + - AVDD28-supply     : Analog power supply regulator on AVDD28 pin
> > > > > > > > > > >
> > > > > > > > > > > I think we normally use lower case in DT bindings and rarely encode
> > > > > > > > > > > voltage in the supply name unless we are dealing with several supplies
> > > > > > > > > > > of the same kind, but I'll let Ron comment on this.
> > > > > > > > > >
> > > > > > > > > > Yes on lowercase though there are some exceptions.
> > > > > > > > > >
> > > > > > > > > > There's also a AVDD22 supply as well as DVDD12 and VDDIO. So we
> > > > > > > > > > probably need to keep the voltage, but the binding is incomplete.
> > > > > > > > >
> > > > > > > > > What is incomplete here? can you please elaborate.
> > > > > > > >
> > > > > > > > You are missing the 3 other supplies the chip has: AVDD22, DVDD12 and VDDIO.
> > > > > > >
> > > > > > > Though it has other supplies, only AVDD28 is connected in the Host
> > > > > > > interface design similar like 9. Reference Schematic on Page, 23 in
> > > > > > > attached manual.
> > > > > >
> > > > > > That is for a particular board design. It still has other supplies.
> > > > > > Just make the binding complete please. You can make them optional. I
> > > > > > don't care if the driver supports controlling all the supplies or not
> > > > > > (though Dmitry might).
> > > > >
> > > > > So, Can I make bulk get and enable in all 4 regulators global to
> > > > > driver or specific to that chip, in either way the regulators which
> > > > > are not used to process via dummy regulators (which we all know).
> > > > >
> > > > > or regulator which are not using are get via devm_regulator_get_optional.
> > > > >
> > > > > Any suggestions?
> > > >
> > > > Just realized to go with bulk calls, please have a look at on v5 [1]
> > >
> > > I do not believe you can use bulk regulator API here as you need to
> > > implement the power up timing scheme mentioned on p. 12 of the spec you
> > > referenced earlier. And, because of that timing diagram, I believe if
> > > you want to control AVDD supply, you also have to control VDDIO supply
> > > as it has to be on only after enabling AVDD.
> >
> > AVDD here is AVDD28 it' is an out name of pin (mentioned in p. 23). So
> > the power scheme goes to enable AVDD28 and then VDDIO does that really
> > mean bulk of two regulators?
> 
> The time between these two regulator operations is nearly 0, as per
> power scheme diagram T1 >= 0us. I think I can use bulk since there is
> no necessity of delay between these two regulator operations.
> 
> What do you think?

Does the bulk enable provide any guarantees as to the order of
operations? If it does not then I think we should ensure that they are
powered up/down in the right order.

Thanks.

-- 
Dmitry