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

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Date:   Thu, 12 Nov 2020 20:03:50 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>,
        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()

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?

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>
>>> ---
>>>