linux-kernel - Re: [PATCH v1 1/2] platform/x86: int3472: add hpd pin support

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Message-ID: <750048e9-292a-4960-9fb2-76ce21db1811@intel.com>
Date: Mon, 14 Apr 2025 18:01:13 +0800
From: "Yan, Dongcheng" <dongcheng.yan@...el.com>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>,
 "Yan, Dongcheng" <dongcheng.yan@...ux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Hans de Goede <hdegoede@...hat.com>, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, hverkuil@...all.nl,
 u.kleine-koenig@...libre.com, ricardo.ribalda@...il.com,
 bingbu.cao@...ux.intel.com, hao.yao@...el.com
Subject: Re: [PATCH v1 1/2] platform/x86: int3472: add hpd pin support

Hi Sakari,

On 4/14/2025 4:52 PM, Sakari Ailus wrote:
> Hi Dongcheng,
> 
> On Mon, Apr 14, 2025 at 04:40:26PM +0800, Yan, Dongcheng wrote:
>> Hi Andy,
>>
>> On 4/14/2025 4:11 PM, Andy Shevchenko wrote:
>>> On Mon, Apr 14, 2025 at 03:52:50PM +0800, Yan, Dongcheng wrote:
>>>> On 4/11/2025 4:33 PM, Hans de Goede wrote:
>>>>> On 11-Apr-25 10:23 AM, Dongcheng Yan wrote:
>>>
>>> ...
>>>
>>>>>> +	case INT3472_GPIO_TYPE_HOTPLUG_DETECT:
>>>>>> +		*con_id = "hpd";
>>>>>> +		*gpio_flags = GPIO_LOOKUP_FLAGS_DEFAULT;
>>>>>
>>>>> This looks wrong, we really need to clearly provide a polarity
>>>>> here since the ACPI GPIO resources do not provide one.
>>>>>
>>>> I tested gpio_flags=GPIO_LOOKUP_FLAGS_DEFAULT/HIGH/LOW, the lt6911uxe
>>>> driver can pass the test and work normally.
>>>
>>> I doubt you tested that correctly. It's impossible to have level triggered
>>> event to work with either polarity. It might be also a bug in the code lurking
>>> somewhere, but it would be unlikely (taking into account amount of systems
>>> relying on this).
>>>
>>> Is it edge triggered event?
>>>
>>
>> It is an edge triggered event in lt6911uxe. In order to better adapt to
>> other uses, "hpd" is meaningful to specify a polarity here.
>>
>> In lt6911uxe, GPIO "hpd" is used as irq, and set irq-flag to
>> IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT. So no matter
>> rising or falling, driver can work normally.
>> "
>> ret = request_threaded_irq(gpiod_to_irq(lt6911uxe->irq_gpio),	NULL,
>> lt6911uxe_threaded_irq_fn, IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
>> IRQF_ONESHOT, NULL, lt6911uxe);
>> "
> 
> include/linux/gpio/machine.h:
> 
> 	GPIO_PERSISTENT                 = (0 << 3),
> ...
> 	GPIO_LOOKUP_FLAGS_DEFAULT       = GPIO_ACTIVE_HIGH | GPIO_PERSISTENT,
> 
> I.e. you effectively have GPIO_ACTIVE_HIGH there.
> 
> Btw. no need to cc this set to stable@...r.kernel.org, I've dropped it from
> the cc list. See Documentation/process/submitting-patches.rst .
> 

Thanks, I will remove it in a subsequent email.

Thanks,
Dongcheng