linux-kernel - Re: [PATCH V6 01/21] irqchip: tegra: Do not disable COP IRQ during suspend

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Date:   Thu, 25 Jul 2019 13:59:09 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Peter De Schrijver <pdeschrijver@...dia.com>
Cc:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, tglx@...utronix.de,
        jason@...edaemon.net, marc.zyngier@....com,
        linus.walleij@...aro.org, stefan@...er.ch, mark.rutland@....com,
        pgaikwad@...dia.com, sboyd@...nel.org, linux-clk@...r.kernel.org,
        linux-gpio@...r.kernel.org, jckuo@...dia.com, josephl@...dia.com,
        talho@...dia.com, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, mperttunen@...dia.com,
        spatra@...dia.com, robh+dt@...nel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH V6 01/21] irqchip: tegra: Do not disable COP IRQ during
 suspend

25.07.2019 13:38, Peter De Schrijver пишет:
> On Thu, Jul 25, 2019 at 01:33:48PM +0300, Peter De Schrijver wrote:
>> On Thu, Jul 25, 2019 at 01:05:13PM +0300, Dmitry Osipenko wrote:
>>> 25.07.2019 12:55, Peter De Schrijver пишет:
>>>> On Mon, Jul 22, 2019 at 12:54:51PM +0300, Dmitry Osipenko wrote:
>>>>>
>>>>> All Tegra SoCs support SC7, hence the 'supports_sc7' and the comment
>>>>> doesn't sound correct to me. Something like 'firmware_sc7' should suit
>>>>> better here.
>>>>>
>>>>>> +			writel_relaxed(~0ul, ictlr + ICTLR_COP_IER_CLR);
>>>>>
>>>>> Secondly, I'm also not sure why COP interrupts need to be disabled for
>>>>> pre-T210 at all, since COP is unused. This looks to me like it was
>>>>> cut-n-pasted from downstream kernel without a good reason and could be
>>>>> simply removed.
>>>>
>>>> I don't think we can rely on the fact that COP is unused. People can
>>>> write their own code to run on COP.
>>>
>>> 1. Not upstream - doesn't matter.
>>>
>>
>> The code is not part of the kernel, so obviously it's not upstream?
>>
>>> 2. That's not very good if something unknown is running on COP and then
>>> kernel suddenly intervenes, don't you think so?
>>
>> Unless the code was written with this in mind.
>>

In that case, please see 1. ;)

> 
> Looking at this again, I don't think we need to enable the IRQ at all.

Could you please clarify? The code only saves/restores COP's interrupts
context across suspend-resume.

Again, that's absolutely useless code for the upstream kernel which
could be removed safely to avoid the confusion, IMHO. I can type a patch
if you're agreeing.