linux-kernel - Re: [PATCH 12/12] arm64: dts: exynos: Add Exynos850 SoC support

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Date:   Thu, 05 Aug 2021 08:30:30 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     Sam Protsenko <semen.protsenko@...aro.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
        Ryu Euiyoul <ryu.real@...sung.com>,
        Tom Gall <tom.gall@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH 12/12] arm64: dts: exynos: Add Exynos850 SoC support

On Thu, 05 Aug 2021 08:17:14 +0100,
Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com> wrote:
> 
> On 04/08/2021 23:30, Sam Protsenko wrote:
> >>>
> >>> Nice catch! Actually there is an error (typo?) in SoC's TRM, saying
> >>> that Virtual Interface Control Register starts at 0x3000 offset (from
> >>> 0x12a00000), where it obviously should be 0x4000, that's probably
> >>> where this dts error originates from. Btw, I'm also seeing the same
> >>> error in exynos7.dtsi.
> >>
> >> What's the error exactly? The "Virtual interface control register"
> >> offset (3rd region) is set properly to 0x4000 on Exynos7. Also one for
> >> the Exynos5433 looks correct.
> >>
> > 
> > The issue is that 2nd region's size is 0x1000, but it must be 0x2000.
> > It's defined by GIC-400 architecture, as I understand. Please look at
> > [1], table 3-1 has very specific offsets and sizes for each functional
> > block, and each particular SoC must adhere to that spec. So having
> > 0x1000 for 2nd region can't be correct. And because exynos7.dtsi has
> > GIC-400 as well, and 0x1000 is specified there for 2nd region size
> > too, so I presume there is the same mistake there.
> 
> I understand, the range length has indeed same mistake. However it does
> not matter that much There are no registers pass 0x10C (so pass 0x1000).
> This address space is not used.

I have no idea which spec you are looking at, but the GICv2
architecture (of which GIC400 is an implementation) definitely has a
register in the second 4kB page of the CPU interface. It contains the
GICC_DIR register, which is used to deactivate an interrupt when
EOIMode==1.

Linux actively uses it when started at EL2.

	M.

-- 
Without deviation from the norm, progress is not possible.