linux-kernel - Re: Suspend-resume failure on Intel Eagle Lake Core2Duo

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Message-ID: <CAK7LNAQ05=5Tj6fhwx-DJQNsDfwKdoH5PJKFdwTQofB=3Ppgcg@mail.gmail.com>
Date:   Mon, 7 Aug 2017 13:45:44 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Tomi Sarvela <tomi.p.sarvela@...el.com>,
        Martin Peres <martin.peres@...ux.intel.com>,
        Jeffy Chen <jeffy.chen@...k-chips.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Suspend-resume failure on Intel Eagle Lake Core2Duo

Hi Marc,


2017-08-03 22:30 GMT+09:00 Marc Zyngier <marc.zyngier@....com>:
> On 03/08/17 13:52, Masahiro Yamada wrote:
>> Hi Marc,
>>
>> 2017-08-03 17:41 GMT+09:00 Marc Zyngier <marc.zyngier@....com>:
>>> Hi Masahiro,
>>>
>>> On 03/08/17 08:32, Masahiro Yamada wrote:
>>>> Hi.
>>>>
>>>> 2017-08-01 0:55 GMT+09:00 Thomas Gleixner <tglx@...utronix.de>:
>>>>> On Mon, 31 Jul 2017, Tomi Sarvela wrote:
>>>>>> On 31/07/17 18:06, Thomas Gleixner wrote:
>>>>>>> Can you please remove the patch. And try the following:
>>>>>>>
>>>>>>> # echo N > /sys/module/printk/parameters/console_suspend
>>>>>>>
>>>>>>> # echo mem > /sys/power/state
>>>>>>>
>>>>>>> and log the output of the serial console. That way we might get a clue
>>>>>>> where it gets stuck.
>>>>>>
>>>>>> I'm afraid it hangs right away. No response from SSH, no output to serial.
>>>>>
>>>>> What means hangs right away? Is there no output at all on the serial
>>>>> console? Or does it just stop at some point?
>>>>>
>>>>> Thanks,
>>>>>
>>>>>         tglx
>>>>>
>>>>
>>>> Sorry for jumping in.
>>>> Finally, I found this thread.
>>>>
>>>>
>>>> My environment is completely different (ARM64 board),
>>>> I am also suffering from a hibernation problem
>>>> since this commit.
>>>>
>>>>
>>>> I get no response on the serial console
>>>> after "Restarting tasks ... done." log message.
>>>>
>>>>
>>>> By reverting bf22ff45bed6 ("genirq: Avoid unnecessary low level
>>>> irq function calls", I can get hibernation working again.
>>>>
>>>>
>>>> SW info:
>>>> defconfig:  arch/arm64/configs/defconfig
>>>> DT       :  arch/arm64/boot/dts/socionext/uniphier-ld20-ref.dts
>>>> PSCI     :  ARM Trusted Firmware
>>>>
>>>>
>>>> SoC info:
>>>> CPU      :  Cortex-A72 * 2 + Cortex-A53 * 2
>>>> irqchip  :  GICv3 (drivers/irq/irq-gic-v3.c)
>>>
>>> Let me take an educated guess: It feels like your firmware doesn't
>>> save/restore the GIC context across suspend/resume. Is that something
>>> you could check, assuming you have access to the firmware source code?
>>
>> Thanks for your comments.
>>
>>
>> I do not know much about the manner of preserving GICv3 context.
>>
>> I can see this patch  (rejected?) :
>> https://patchwork.kernel.org/patch/9343061/
>>
>>
>> Is it something that should be completely cared by firmware
>> instead of kernel?
>
> That was definitely the intention, but it looks like something that ATF
> has only started supporting very recently:
>
> https://github.com/ARM-software/arm-trusted-firmware/pull/1047
>
>> ARM Trusted Firmware (https://github.com/ARM-software/arm-trusted-firmware)
>> is open source software, and I pushed my platform code to the upstream.
>>
>> So, yes, I (and everybody) can have access to the firmware source code.
>>
>>
>> I am not sure how ATF saves the context during hibernation, though.
>
> See the above link. Is there any chance of you trying this into your
> firmware?
>
> Thanks,

Thanks for the pointer.


Yes.  I will try that once GIC-v3 context save/restore is supported in ATF.

I think that will basically work for suspend-to-ram
because all contexts including both non-secure and secure worlds will
be retained in the main memory.

However, I still do not understand how the context is preserved during
the hibernation (suspend-to-disk).


If my understanding is correct, hibernation on Linux works like follows:

[1] Freeze all tasks
[2] CPU_OFF for non-boot CPUs
[3] Create a hibernation image
[4] CPU_ON for non-boot CPUs
[5] Write the hibernation image to the disk (=swap area)
[6] SYSTEM_OFF


IIUC, [5] only writes the context Linux takes care of (only non-secure).

If so, where and how does the firmware write the GIC-v3 context
to the disk?


-- 
Best Regards
Masahiro Yamada