linux-kernel - Re: [PATCH v3 4/5] rtc: mt6397: Remove start time parameters

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Message-ID: <968001f7-96d1-4ad5-8c36-28cac5dc30f1@collabora.com>
Date: Mon, 14 Apr 2025 13:09:14 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Alexandre Mergnat <amergnat@...libre.com>
Cc: Eddie Huang <eddie.huang@...iatek.com>, Sean Wang
 <sean.wang@...iatek.com>, Matthias Brugger <matthias.bgg@...il.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, linux-rtc@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 4/5] rtc: mt6397: Remove start time parameters

Il 11/04/25 15:39, Alexandre Belloni ha scritto:
> On 11/04/2025 15:36:12+0200, Alexandre Belloni wrote:
>> On 11/04/2025 14:35:57+0200, Alexandre Mergnat wrote:
>>> The start time parameters is currently hardcoded to the driver, but
>>> it may not fit with all equivalent RTC that driver is able to support.
>>>
>>> Remove the start_secs and set_start_time value setup because it
>>> will be handled by the rtc_device_get_offset function using the
>>> start-year DTS property.
>>>
>>> Signed-off-by: Alexandre Mergnat <amergnat@...libre.com>
>>> ---
>>>   drivers/rtc/rtc-mt6397.c | 2 --
>>>   1 file changed, 2 deletions(-)
>>>
>>> diff --git a/drivers/rtc/rtc-mt6397.c b/drivers/rtc/rtc-mt6397.c
>>> index 692c00ff544b2..d47626d47602f 100644
>>> --- a/drivers/rtc/rtc-mt6397.c
>>> +++ b/drivers/rtc/rtc-mt6397.c
>>> @@ -291,8 +291,6 @@ static int mtk_rtc_probe(struct platform_device *pdev)
>>>   	rtc->rtc_dev->ops = &mtk_rtc_ops;
>>>   	rtc->rtc_dev->range_min = RTC_TIMESTAMP_BEGIN_1900;
>>>   	rtc->rtc_dev->range_max = mktime64(2027, 12, 31, 23, 59, 59);
>>> -	rtc->rtc_dev->start_secs = mktime64(1968, 1, 2, 0, 0, 0);
>>> -	rtc->rtc_dev->set_start_time = true;
>>>   
>>
>> This is going to break the time for people upgrading their kernel, you
>> are unfortunately stuck with this.
>>
> 
> To be clear, the breakage will happen when upgrading the kernel but not
> the device tree with 5/5
> 

Yes, you're stuck with this. Devicetree has to be retrocompatible.

Besides, this start_secs is what gets used by default, and the start-year
devicetree property should take precedence and effectively override the
start_secs default.

Just keep it there.... :-)

Cheers,
Angelo

>>>   	return devm_rtc_register_device(rtc->rtc_dev);
>>>   }
>>>
>>> -- 
>>> 2.25.1
>>>
>>
>> -- 
>> Alexandre Belloni, co-owner and COO, Bootlin
>> Embedded Linux and Kernel engineering
>> https://bootlin.com
>