From: Aswath Govindraju <a-govindraju@ti.com>
To: Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Roger Quadros <rogerq@kernel.org>,
Rob Herring <robh+dt@kernel.org>
Cc: Vignesh Raghavendra <vigneshr@ti.com>,
Kishon Vijay Abraham I <kishon@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.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: Thu, 9 Jun 2022 11:03:32 +0530 [thread overview]
Message-ID: <1eccfcf6-085b-4b9c-8efd-861b66a08287@ti.com> (raw)
In-Reply-To: <f714ee55-ef47-317d-81b9-57020dda064b@ti.com>
Hi Rob,
On 02/05/22 11:00, Aswath Govindraju wrote:
> Hi Rob,
>
> On 26/04/22 12:27, Heikki Krogerus wrote:
>> 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.
>>
>
> A gentle ping regarding this.
>
A gentle ping regarding the above question.
Thanks,
Aswath
> Thanks,
> Aswath
>
>> 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
>>>>
>>>>
>>
--
Thanks,
Aswath
next prev parent reply other threads:[~2022-06-09 5:34 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
2022-05-02 5:30 ` Aswath Govindraju
2022-06-09 5:33 ` Aswath Govindraju [this message]
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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