From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
To: Roger Quadros <rogerq@kernel.org>
Cc: Aswath Govindraju <a-govindraju@ti.com>,
Vignesh Raghavendra <vigneshr@ti.com>,
Kishon Vijay Abraham I <kishon@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Sven Peter <sven@svenpeter.dev>,
Alyssa Rosenzweig <alyssa@rosenzweig.io>,
Hector Martin <marcan@marcan.st>,
Martin Kepplinger <martink@posteo.de>,
Bryan O'Donoghue <bryan.odonoghue@linaro.org>,
linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: usb: tps6598x: Make the interrupts property optional
Date: Tue, 26 Apr 2022 09:57:07 +0300 [thread overview]
Message-ID: <YmeXw8nerjpuKPC9@kuha.fi.intel.com> (raw)
In-Reply-To: <89f7d69a-4fc8-33cc-d9ca-5c50dc5381ab@kernel.org>
On Tue, Apr 26, 2022 at 09:42:31AM +0300, Roger Quadros wrote:
> Hi,
>
> On 22/04/2022 08:07, Aswath Govindraju wrote:
> > Hi Roger,
> >
> > On 21/04/22 00:46, Roger Quadros wrote:
> >> Hi,
> >>
> >> On 18/04/2022 08:19, Aswath Govindraju wrote:
> >>> Hi Roger,
> >>>
> >>> On 14/04/22 23:40, Roger Quadros wrote:
> >>>> Hi,
> >>>>
> >>>> On 14/04/2022 11:31, Aswath Govindraju wrote:
> >>>>> Support for polling has been added in the driver, which will be used by
> >>>>> default if interrupts property is not populated. Therefore, remove
> >>>>> interrupts and interrupt-names from the required properties and add a note
> >>>>> under interrupts property describing the above support in driver.
> >>>>>
> >>>>> Suggested-by: Roger Quadros <rogerq@kernel.org>
> >>>>
> >>>> I did not suggest to make interrupts optional by default.
> >>>>
> >>>> What I suggested was that if a DT property exists to explicitly
> >>>> indicate polling mode then interrupts are not required.
> >>>>
> >>>
> >>> ohh okay, got it. However, may I know if adding a dt property to
> >>> indicate polling for aiding the driver, is the correct approach to model it?
> >>>
> >>> In terms of modelling hardware, as interrupts are not connected we are
> >>> not populating the interrupts property. Shouldn't that be all. If we are
> >>> adding a property explicitly to indicate polling that can be used by
> >>> driver, wouldn't that be a software aid being added in the device tree?
> >>
> >> The hardware (tps6598x chip) has an interrupt pin and is expected to be used
> >> in normal case.
> >>
> >> Some buggy boards might have forgot to connect it. We are adding polling mode only for these buggy boards. ;)
> >> So polling mode is an exception.
> >>
> >
> > Yes as you mentioned the interrupt line is expected to connected but
> > there could be cases where there are not enough pins on the SoC and
> > polling is used intentionally. In these cases this would be a feature
> > rather than a bug.
>
> I do not agree that this is a feature but a board defect. You can always use
> a GPIO expander to add more GPIOs than the SoC can provide.
>
> Type-C events are asynchronous and polling is a waste of CPU time.
> What will you do if system suspends and you need to wake up on Type-C
> status change?
> So polling mode is just an exception for the defective boards or could
> be used for debugging.
>
> >
> > Also, I feel like not adding interrupts property in the dt nodes will
> > indicate polling. My question is why are we adding an extra property
> > (which is being used only as an aid in the driver) when this feature can
> > be modeled by making interrupts property optional.
>
> Because interrupt property was not originally optional for this driver.
>
> I would like to hear what Heikki has to say about this.
>
> Any thoughts Heikki?
I think the question is generic. How should DT describe the
connection/lack of connection? Rob should comment on this.
thanks,
> cheers,
> -roger
>
> >
> > Thanks,
> > Aswath
> >
> >> cheers,
> >> -roger
> >>
> >>>
> >>> Thanks,
> >>> Aswath
> >>>
> >>>>> Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
> >>>>> ---
> >>>>> Documentation/devicetree/bindings/usb/ti,tps6598x.yaml | 4 ++--
> >>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
> >>>>>
> >>>>> diff --git a/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml b/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml
> >>>>> index a4c53b1f1af3..1c4b8c6233e5 100644
> >>>>> --- a/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml
> >>>>> +++ b/Documentation/devicetree/bindings/usb/ti,tps6598x.yaml
> >>>>> @@ -25,6 +25,8 @@ properties:
> >>>>>
> >>>>> interrupts:
> >>>>> maxItems: 1
> >>>>> + description:
> >>>>> + If interrupts are not populated then by default polling will be used.
> >>>>>
> >>>>> interrupt-names:
> >>>>> items:
> >>>>> @@ -33,8 +35,6 @@ properties:
> >>>>> required:
> >>>>> - compatible
> >>>>> - reg
> >>>>> - - interrupts
> >>>>> - - interrupt-names
> >>>>>
> >>>>> additionalProperties: true
> >>>>>
> >>>>
> >>>> cheers,
> >>>> -roger
> >
> >
--
heikki
next prev parent reply other threads:[~2022-04-26 6:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 8:31 [PATCH 0/2] typec: tipd: Add support for polling Aswath Govindraju
2022-04-14 8:31 ` [PATCH 1/2] dt-bindings: usb: tps6598x: Make the interrupts property optional Aswath Govindraju
2022-04-14 18:10 ` Roger Quadros
2022-04-18 5:19 ` Aswath Govindraju
2022-04-20 19:16 ` Roger Quadros
2022-04-22 5:07 ` Aswath Govindraju
2022-04-26 6:42 ` Roger Quadros
2022-04-26 6:57 ` Heikki Krogerus [this message]
2022-05-02 5:30 ` Aswath Govindraju
2022-06-09 5:33 ` Aswath Govindraju
2022-04-14 8:31 ` [PATCH 2/2] usb: typec: tipd: Add support for polling interrupts status when interrupt line is not connected Aswath Govindraju
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