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Subject: Re: [PATCH v4 2/2] gpio: sch: Hook into ACPI SCI handler to catch
 GPIO edge events
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
        Andy Shevchenko <andy@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
References: <20210316162613.87710-1-andriy.shevchenko@linux.intel.com>
 <20210316162613.87710-3-andriy.shevchenko@linux.intel.com>
 <YFEZ6GYuXGaX/LP2@smile.fi.intel.com>
 <a3a6c80a-724c-e2fb-9597-b14a302c5ff4@siemens.com>
 <YFHRWm6YIh9NU1I/@smile.fi.intel.com>
From:   Jan Kiszka <jan.kiszka@siemens.com>
Message-ID: <86f3a770-3b90-5fdb-7811-789118dad375@siemens.com>
Date:   Wed, 17 Mar 2021 10:57:39 +0100
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On 17.03.21 10:52, Andy Shevchenko wrote:
> On Wed, Mar 17, 2021 at 07:57:44AM +0100, Jan Kiszka wrote:
>> On 16.03.21 21:49, Andy Shevchenko wrote:
>>> On Tue, Mar 16, 2021 at 06:26:13PM +0200, Andy Shevchenko wrote:
>>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>>
>>>> Neither the ACPI description on the Quark platform provides the required
>>>> information is to do establish generic handling nor hardware capable of
>>>> doing it. According to the datasheet the hardware can generate SCI events.
>>>> Therefore, we need to hook from the driver directly into SCI handler of
>>>> the ACPI subsystem in order to catch and report GPIO-related events.
>>>>
>>>> Validated on the Quark-based IOT2000 platform.
>>>
>>> This patch must be dropped completely. SCI handler is not correct way to do
>>> this. The proper way (and we have already few examples in the kernel) is to
>>> register GPE event.
>>
>> As explained above, this is not supported by the preexisting firmware,
>> and there won't be any updates to it anymore.
>>
>> This platform is history, the SoC was discontinued by Intel long ago,
>> and our devices reaching their support end as well. The race to upstream
>> was lost in this case - backlog too long, we being too slow.
> 
> So you have no device to test and there is actually no device which has this
> capability in the wild.
> 
> Am I reading this correct?

No. We do have devices but we don't have the time to invest further into
bringing missing features upstream - not to speak of changing the
firmware in order to support cleaner upstream integration.

For the remaining lifetime of the devices, we are stuck on 4.4.y-cip
with a few additional patches, including this one.

> 
> In any case, we have platforms in the wild that actually support GPEs and this
> makes sense for them.

Sure, I don't want to judge for them. Just our original target of this
patch is no longer relevant for upstream.

Jan

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