linux-kernel - Re: [PATCH] MIPS: Loongson64: Add read_persistent

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Date:   Fri, 13 Nov 2020 16:24:37 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhc@...ote.com>
CC:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Yinglu Yang <yangyinglu@...ngson.cn>,
        WANG Xuerui <git@...0n.name>
Subject: Re: [PATCH] MIPS: Loongson64: Add read_persistent_clock64()



于 2020年11月13日 GMT+08:00 上午11:41:01, Tiezhu Yang <yangtiezhu@...ngson.cn> 写到:
>On 11/13/2020 10:21 AM, Jiaxun Yang wrote:
>>
>>
>> 在 2020/11/12 20:03, Tiezhu Yang 写道:
>>> On 11/12/2020 06:09 PM, Jiaxun Yang wrote:
>>>>
>>>>
>>>> 在 2020/11/12 18:04, Jiaxun Yang 写道:
>>>>> Hi Tiezhu,
>>>>>
>>>>> 在 2020/11/12 16:29, Tiezhu Yang 写道:
>>>>>> Add read_persistent_clock64() to read the time from the battery 
>>>>>> backed
>>>>>> persistent clock. With this patch, we can fix the wrong time issue 
>>>>>> due
>>>>>> to the system clock is not consistent with hardware clock after 
>>>>>> resume
>>>>>> from sleep state S3 (suspend to RAM), at the same time, the system 
>>>>>> time
>>>>>> can be right instead of "Thu Jan 1 08:00:00 CST 1970" without rtc 
>>>>>> driver.
>>>>>>
>>>>>> start_kernel()
>>>>>>    timekeeping_init()
>>>>>>      read_persistent_wall_and_boot_offset()
>>>>>>        read_persistent_clock64()
>>>>>>
>>>>>> timekeeping_resume()
>>>>>>    read_persistent_clock64()
>>>>>>
>>>>>> timekeeping_suspend()
>>>>>>    read_persistent_clock64()
>>>>>
>>>>> It is highly discoraged to do anything with bridgetype, which isn't 
>>>>> probed via
>>>>> devicetree.
>>>>>
>>>>> Please check if you can deal with that inside RTC framework, or 
>>>>> make it as
>>>>> a part of RTC driver (e.g. set up a callback).
>>>>>
>>>>> Also you should submit RTC driver at first if you intend to 
>>>>> complete LS7A support.
>>>>
>>>> Oops,
>>>> Just dig it deeper, I guess simply select RTC_HCTOSYS would solve 
>>>> the issue.
>>>> We're trying very hard to decouple all the drivers and conponents,
>>>> DeviceTree for all!
>>>
>>> +cc WANG Xuerui <git@...0n.name>
>>>
>>> Hi Jiaxun,
>>>
>>> Thanks for your reply.
>>>
>>> Xuerui has already submitted the patch of LS7A rtc driver [1],
>>> but not yet been merged into the mainline kernel, I discussed
>>> with him early today.
>>>
>>> Do you mean that read_persistent_clock64() can call the function
>>> like rtc_read_time() defined in rtc driver?
>>
>> I do think select RTC_HCTOSYS after getting RTC driver applied can help.
>
>Yes, I agree.
>
>> What's your point to have read_persistent_clock64 for Loongson64?
>
>(1) Currently, the LS7A RTC driver has not been merged into the
>mainline kernel, read_persistent_clock64() is useful in the following
>call path:
>
>start_kernel()
>    timekeeping_init()
>      read_persistent_wall_and_boot_offset()
>        read_persistent_clock64()
>
>(2) When the LS7A RTC driver is merged into the mainline kernel
>some time later, if RTC_HCTOSYS and RTC_DRV_LS2X are not set,
>read_persistent_clock64() is also useful unless RTC_HCTOSYS
>and RTC_DRV_LS2X are set by default in Kconfig instead of
>loongson3_defconfig.
>
>So I think read_persistent_clock64() looks like a backup function.

Still can't understand why this kind of backup is necessary.
If you wish to help please help with the RTC driver.

Duplication is not the way we work.
Please try to learn common solutions, all others are doing so.

Thanks

- Jiaxun


>
>>
>> Thanks
>>
>> - Jiaxun
>>
>>>
>>> Thanks,
>>> Tiezhu
>>>
>>> [1] 
>>> https://patchwork.kernel.org/project/linux-mips/patch/20200923075845.360974-2-git@xen0n.name/
>>>
>>>>
>>>>>
>>>>> Thanks.
>>>>>
>>>>> - Jiaxun
>>>>>
>>>>>>
>>>>>> Signed-off-by: Yinglu Yang <yangyinglu@...ngson.cn>
>>>>>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>>>>>> ---
>>>>>>