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    SubjectRe: [PATCH 1/2] dt-bindings: usb: tps6598x: Make the interrupts property optional
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    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?

    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
    >
    >

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