linux-kernel - Re: [PATCH v1 2/3] rtc: mt6359: Add RTC hardware range and add support for start-year

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Message-ID: <247abc15-d82f-3e8f-5202-edc6099707df@mediatek.com>
Date: Tue, 24 Sep 2024 15:05:36 +0800
From: Macpaul Lin <macpaul.lin@...iatek.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	<lee@...nel.org>, <ZhanZhan.ge@...iatek.com>
CC: <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
	<matthias.bgg@...il.com>, <eddie.huang@...iatek.com>,
	<sean.wang@...iatek.com>, <alexandre.belloni@...tlin.com>,
	<sen.chu@...iatek.com>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-mediatek@...ts.infradead.org>, <linux-rtc@...r.kernel.org>,
	<kernel@...labora.com>, <yong.mao@...iatek.com>
Subject: Re: [PATCH v1 2/3] rtc: mt6359: Add RTC hardware range and add
 support for start-year


On 9/24/24 12:08, Macpaul Lin wrote:
> 
> On 9/23/24 18:00, AngeloGioacchino Del Regno wrote:
>> Add the RTC hardware range parameters to enable the possibility
>> of using the `start-year` devicetree property which, if present,
>> will set the start_secs parameter by overriding the defaults
>> that this driver is setting;
>>
>> To keep compatibility with (hence have the same date/time reading
>> as) the old behavior, set:
>>   - range_min to 1900-01-01 00:00:00
>>   - range_max to 2027-12-31 23:59:59 (HW year max range is 0-127)
>>   - start_secs defaulting to 1968-01-02 00:00:00
>>
>> Please note that the oddness of starting from January 2nd is not
>> a hardware quirk and it's done only to get the same date/time
>> reading as an RTC which time was set before this commit.
>>
>> Also remove the RTC_MIN_YEAR_OFFSET addition and subtraction in
>> callbacks set_time() and read_time() respectively, as now this
>> is already done by the API.
>>
>> Signed-off-by: AngeloGioacchino Del Regno 
>> <angelogioacchino.delregno@...labora.com>
>> ---
>>   drivers/rtc/rtc-mt6397.c | 13 ++++---------
>>   1 file changed, 4 insertions(+), 9 deletions(-)
> 
> [snip]
> 
> Thanks for helping add new patch fix for RTC.
> 
>> @@ -302,6 +293,10 @@ static int mtk_rtc_probe(struct platform_device 
>> *pdev)
>>       device_init_wakeup(&pdev->dev, 1);
>>       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;
>>       return devm_rtc_register_device(rtc->rtc_dev);
>>   }
> 
> Dear @Zhanhan, Please help to leave comment if you think there is 
> something need to be clarify. For example, I've found some relate origin 
> defines
> in "include/linux/mfd/mt6397/rtc.h"
> #define RTC_MIN_YEAR    1968
> #define RTC_BASE_YEAR    1900
> #define RTC_NUM_YEAR    128
> #define RTC_MIN_YEAR_OFFSET    (RTC_MIN_YEAR - RTC_BASE_YEAR)
> 
> Should MediaTek remove RTC_MIN_YEAR and RTC_BASE_YEAR in next patch?
> And since there may not exist any smartphone/tablet/TV using mt6397
> RTC earlier than 2010? Is it possible to change
> RTC_TIMESTAMP_BEGIN_1900 to RTC_TIMESTAMP_BEGIN_2000 without breaking
> compatibility for these devices?
> 
> Thanks
> Macpaul Lin
> 

After discussing these change with ZhanZhan, MediaTek think use 
RTC_TIMESTAMP_BEGIN_1900 and the other changes are okay.

Reviewed-by: Macpaul Lin <macpaul.lin@...iatek.com>
Reviewed-by: ZhanZhan Ge <zhanzhan.ge@...iatek.com>

Thanks!
Macpaul Lin