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

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Message-ID: <20190802130537.GB3883@pdeschrijver-desktop.Nvidia.com>
Date:   Fri, 2 Aug 2019 16:05:37 +0300
From:   Peter De Schrijver <pdeschrijver@...dia.com>
To:     Dmitry Osipenko <digetx@...il.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

On Thu, Jul 25, 2019 at 01:59:09PM +0300, Dmitry Osipenko wrote:
> 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. ;)
> 

In general the kernel should not touch the COP interrupts I think.

> > 
> > 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.

The sc7 entry firmware doesn't use interrupts.

Peter.