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

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Date:   Fri, 13 Nov 2020 10:21:52 +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()



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.
What's your point to have read_persistent_clock64 for Loongson64?

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>
>>>> ---
>>>>