linux-kernel - Re: [PATCH] rtc: rtc-pm8xxx: control default alarm wake up capability

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Date:   Mon, 7 Aug 2023 10:26:37 +0530
From:   Anvesh Jain P <quic_ajainp@...cinc.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
CC:     Alessandro Zummo <a.zummo@...ertech.it>,
        <linux-rtc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Venkata Rao Kakani <quic_vkakani@...cinc.com>
Subject: Re: [PATCH] rtc: rtc-pm8xxx: control default alarm wake up capability



On 8/3/2023 7:10 PM, Alexandre Belloni wrote:
> On 03/08/2023 15:39:41+0200, Alexandre Belloni wrote:
>> On 03/08/2023 19:01:51+0530, Anvesh Jain P wrote:
>>>
>>>
>>> On 8/2/2023 1:04 AM, Alexandre Belloni wrote:
>>>> On 01/08/2023 18:18:46+0530, Anvesh Jain P wrote:
>>>>> In automotive systems, RTC should not wake up the device when it is parked
>>>>> or when it is garage to avoid leakage current. providing a control from
>>>>> device tree to avoid RTC wake up based on the use case is reason for this
>>>>> patch.
>>>>>
>>>>
>>>> Then simply avoid providing an IRQ or setting an alarm.
>>> The purpose of the change is just to block alarms/notifications waking up
>>> the target when it is in Suspend2ram(low power) mode.
>>> if we disable IRQ, alarms/notifications won't come even when the target is
>>> in active mode.
>>> This change will just stop the wake up capability of the alarm when target
>>> is in suspend 2 ram mode based on flag passed from device tree.
>>> Use case of this patch is,
>>> In mobile targets where alarms / notifications will need to wake up the
>>> target when there is a reminder as per user expectation.
>>> where as in automotive targets, when driver is not in Car and target is in
>>> suspend state, alarms/notifications would have no meaning and waking up the
>>> target of no use as there is no user to attend the message. hence blocking
>>> them in automotive use cases based on device tree is the use of this patch.
>>
>> Simply remove the alarm before going to suspend, this is a userspace
>> policy, it has nothing to do in the device or kernel.
> s/device/device tree/ obviously.
> 
How to remove from userspace?, if we remove all alarms from userspace, 
will the alarms expiring after wake up would be restored while target 
resumes from suspend 2 ram?
The change would not change alarms behavior. it blocks all notifications 
causing wake up if "disable-alarm-wakeup" property defined in device 
tree. if it is not defined, current behavior of alarm won't change.
>>
>>>>
>>>>> On 8/1/2023 6:10 PM, Alexandre Belloni wrote:
>>>>>> On 01/08/2023 17:15:49+0530, Anvesh Jain P wrote:
>>>>>>> Enable & disable rtc alarm wake up capability based on
>>>>>>> default parameter passed from device tree.
>>>>>>>
>>>>>>
>>>>>> I see what you are doing but not why this is necessary, NAK.
>>>>>>
>>>>>>> Signed-off-by: Venkata Rao Kakani <quic_vkakani@...cinc.com>
>>>>>>> Signed-off-by: Anvesh Jain P <quic_ajainp@...cinc.com>
>>>>>>> ---
>>>>>>>     drivers/rtc/rtc-pm8xxx.c | 3 +++
>>>>>>>     1 file changed, 3 insertions(+)
>>>>>>>
>>>>>>> diff --git a/drivers/rtc/rtc-pm8xxx.c b/drivers/rtc/rtc-pm8xxx.c
>>>>>>> index f6b779c12ca7..bed57be602b6 100644
>>>>>>> --- a/drivers/rtc/rtc-pm8xxx.c
>>>>>>> +++ b/drivers/rtc/rtc-pm8xxx.c
>>>>>>> @@ -523,6 +523,9 @@ static int pm8xxx_rtc_probe(struct platform_device *pdev)
>>>>>>>     	if (rc)
>>>>>>>     		return rc;
>>>>>>> +	if (of_property_read_bool(pdev->dev.of_node, "disable-alarm-wakeup"))
>>>>>>> +		device_set_wakeup_capable(&pdev->dev, false);
>>>>>>> +
>>>>>>>     	rc = dev_pm_set_wake_irq(&pdev->dev, rtc_dd->alarm_irq);
>>>>>>>     	if (rc)
>>>>>>>     		return rc;
>>>>>>>
>>>>>>> base-commit: 0a8db05b571ad5b8d5c8774a004c0424260a90bd
>>>>>>> -- 
>>>>>>> 2.17.1
>>>>>>>
>>>>>>
>>>>
>>
>> -- 
>> Alexandre Belloni, co-owner and COO, Bootlin
>> Embedded Linux and Kernel engineering
>> https://bootlin.com
>