linux-kernel - Re: [PATCH 1/1] pps: clients: gpio: Bypass edge's direction check when not needed

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Date: Fri, 12 Apr 2024 08:44:08 +0200
From: Rodolfo Giometti <giometti@...eenne.com>
To: Bastien Curutchet <bastien.curutchet@...tlin.com>
Cc: linux-kernel@...r.kernel.org,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, herve.codina@...tlin.com,
 christophercordahi@...ometrics.ca
Subject: Re: [PATCH 1/1] pps: clients: gpio: Bypass edge's direction check
 when not needed

On 11/04/24 14:44, Bastien Curutchet wrote:
> Hi Rodolfo
> 
>>>> diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
>>>> index 2f4b11b4dfcd..f05fb15ed7f4 100644
>>>> --- a/drivers/pps/clients/pps-gpio.c
>>>> +++ b/drivers/pps/clients/pps-gpio.c
>>>> @@ -52,7 +52,9 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
>>>>
>>>>          info = data;
>>>>
>>>> -       rising_edge = gpiod_get_value(info->gpio_pin);
>>>> +       rising_edge = info->capture_clear ? \
>>>> +                       gpiod_get_value(info->gpio_pin) : \
>>>> +                       !info->assert_falling_edge;
>>>>          if ((rising_edge && !info->assert_falling_edge) ||
>>>>                          (!rising_edge && info->assert_falling_edge))
>>>>                  pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
>>>>
>>>> Please, review and test it before resubmitting. :)
>>>>
>>>
>>> I'll try this and send a V2 after my tests, thank you.
>>
>> OK, thanks.
>>
>> However we should think very well about this modification since it could be 
>> the case where we have a device sending both assert and clear events but we 
>> wish to catch just the asserts... in this case we will get doubled asserts!
>>
> 
> My understanding is that clear events are to be captured only when this
> capture_clear boolean is set. If it is not set, the PPS_CAPTURECLEAR
> flag is not added to pps_source_info->mode and get_irqf_trigger_flags()
> will return only one edge flag (rising or falling depending on
> assert-falling-edge DT property).

Yes. You are right.

> By the way, I see that the capture_clear is never set since the legacy
> platform data support has been dropped (commit ee89646619ba).

I see, but it can be re-enabled in the future... In this scenario, I think we 
should add a DT entry to enable this special behavior. Maybe we can also add a 
warning as below:

static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
{
         ...
         if ((rising_edge && !info->assert_falling_edge) ||
                         (!rising_edge && info->assert_falling_edge))
                 pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
         else if (info->capture_clear &&
                         ((rising_edge && info->assert_falling_edge) ||
                         (!rising_edge && !info->assert_falling_edge)))
                 pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data);
	else
		dev_warn_ratelimited(dev, "no ASSERT or CAPTURE event? "
			"Maybe you need support-tiny-assert-pulse?");

         return IRQ_HANDLED;
}

Ciao,

Rodolfo

P.S. I'm sorry, but I'm not good at finding names... ^_^"

-- 
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