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

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Message-ID: <d9cab351-4850-42c7-8fee-a9340d157ed9@linux.intel.com>
Date: Mon, 14 Apr 2025 16:40:26 +0800
From: "Yan, Dongcheng" <dongcheng.yan@...ux.intel.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Hans de Goede <hdegoede@...hat.com>,
 Dongcheng Yan <dongcheng.yan@...el.com>, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, sakari.ailus@...ux.intel.com,
 hverkuil@...all.nl, u.kleine-koenig@...libre.com, ricardo.ribalda@...il.com,
 bingbu.cao@...ux.intel.com, stable@...r.kernel.org, hao.yao@...el.com
Subject: Re: [PATCH v1 1/2] platform/x86: int3472: add hpd pin support

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);
"

Thanks,
Dongcheng