linux-kernel - Re: [PATCH -next] irq-chip/gic-v3-its: Fixed an issue where the ITS executes the residual commands in the queue again when the ITS wakes up from sleep mode.

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Message-ID: <338d65dfeac0cc026c74d9e78ec6f0c1@kernel.org>
Date:   Mon, 09 Nov 2020 10:43:09 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     "xuqiang (M)" <xuqiang36@...wei.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        rui.xiang@...wei.com
Subject: Re: [PATCH -next] irq-chip/gic-v3-its: Fixed an issue where the ITS
 executes the residual commands in the queue again when the ITS wakes up from
 sleep mode.

On 2020-11-09 03:05, xuqiang (M) wrote:
> 在 2020/11/8 0:54, Marc Zyngier 写道:
>> [dropping Jason, whose email address has been bouncing for weeks now]
>> 
>> On 2020-11-07 10:42, Xu Qiang wrote:
>>> On my platform, ITS_FLAGS_SAVE_SUSPEND_STATE is not set,thus do 
>>> nothing
>> 
>> Which platform?
> Hisi Ascend platform
>> 
>>> in its suspend and resuse function.On the other hand,firmware stores
>>> GITS_CTRL,GITS_CBASER,GITS_CWRITER and GITS_BASER<n> in the suspend,
>>> and restores these registers in the resume. As a result, the ITS 
>>> executes
>>> the residual commands in the queue.
>> 
>> Which firmware are you using? I just had a look at the trusted 
>> firmware source
>> code, and while it definitely does something that *looks* like what 
>> you are
>> describing, it doesn't re-enable the ITS on resume.
>> 
>> So what are you running?
> 
> I am using ATF. Since ITS_FLAGS_SAVE_SUSPEND_STATE is not set,ITS
> driver of OS will
> 
> not re-enable ITS in th resume. To make ITS work properly, we changed
> the ATF code
> 
> to re-enable ITS on resume.

I don't think the words "work properly" apply here.

The kernel didn't do what you wanted, so instead of fixing the kernel, 
you
introduced a bug that results in memory corruption from the firmware.

What are you plans to fix your firmware? Because from an upstream ATF
compatibility PoV, all there is to do is to fixup the command queue and
enable the ITS.

         M.
-- 
Jazz is not dead. It just smells funny...