RE: [PATCH] arm64: dts: renesas: r8a7796: Add CMT device nodes

[Biju Das <biju.das@bp.renesas.com>]

Hello Daniel,

Thanks for the feedback.

> -----Original Message-----
> From: Daniel Lezcano <daniel.lezcano@linaro.org>
> Sent: 19 November 2018 17:15
> To: Biju Das <biju.das@bp.renesas.com>; Rob Herring
> <robh+dt@kernel.org>; Mark Rutland <mark.rutland@arm.com>
> Cc: Simon Horman <horms@verge.net.au>; Magnus Damm
> <magnus.damm@gmail.com>; linux-renesas-soc@vger.kernel.org;
> devicetree@vger.kernel.org; Geert Uytterhoeven
> <geert+renesas@glider.be>; Chris Paterson
> <Chris.Paterson2@renesas.com>; Thomas Gleixner <tglx@linutronix.de>;
> John Stultz <john.stultz@linaro.org>; Fabrizio Castro
> <fabrizio.castro@bp.renesas.com>
> Subject: Re: [PATCH] arm64: dts: renesas: r8a7796: Add CMT device nodes
>
> On 19/11/2018 16:50, Biju Das wrote:
> > Hi Daniel,
> >
> > Thanks for the feedback.
> >
> >>>> Subject: Re: [PATCH] arm64: dts: renesas: r8a7796: Add CMT device
> >>>> nodes
> >>>>
> >>>> On 26/10/2018 10:25, Biju Das wrote:
> >>>>> This patch adds CMT{0|1|2|3} device nodes for r8a7796 SoC.
> >>>>>
> >>>>> Signed-off-by: Biju Das <biju.das@bp.renesas.com>
> >>>>> ---
> >>>>> This patch is tested against renesas-dev
> >>>>>
> >>>>> I have executed on inconsistency-check, nanosleep and
> >>>>> clocksource_switch selftests on this arm64 SoC. The
> >>>>> inconsistency-check and nanosleep tests are working fine.The
> >>>>> clocksource_switch asynchronous test is failing due to
> >>>>> inconsistency-check
> >>>> failure on "arch_sys_counter".
> >>>>>
> >>>>> But if i skip the clocksource_switching of "arch_sys_counter", the
> >>>>> asynchronous test is passing for CMT0/1/2/3 timer.
> >>>>>
> >>>>> Has any one noticed this issue?
> >>>>
> >>>> So now that you mention that, I've been through the
> >>>> clocksource_switch on another ARM64 platform (hikey960) and
> >>>> disabled the
> >>>> ARM64_ERRATUM_858921 config option. I can see the same issue.
> >>>>
> >>>> Is this option set on your config ?
> >>>
> >>> No.  As per  " config ARM64_ERRATUM_858921", it is "Workaround for
> >> Cortex-A73 erratum 858921"
> >>>
> >>> Our SoC is 2xCA-57 + 4 x CA-53.  Does  it impact CA-57 + CA_53?
> >>
> >> Dunno :/
> >>
> >>> Any way I will enable this config option and will provide you the results.
> >>
> >> Ok, thanks!
> >
> > The following config is enabled by default on upstream
> > kernel(4.20-rc3) CONFIG_ARM_ARCH_TIMER_EVTSTREAM=y
> > CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND=y
> > CONFIG_FSL_ERRATUM_A008585=y
> > CONFIG_HISILICON_ERRATUM_161010101=y
> > CONFIG_ARM64_ERRATUM_858921=y
> >
> > For a quick testing,  I have activated the erratum using the property
> "fsl,erratum-a008585" on device tree.
> > With this I confirm the issue is fixed.
> >
> > I have  some questions on this.
> > 1) Based  on the test result ,do you think renesas soc also  impacted by the
> ARM64_ERRATUM_858921?
> > 2) Is there any way to find, is this Erratum actually causing the
> asynchronous test to fail?
>
> I guess, you can hack the __fsl_a008585_read_reg macro and check if the
> invalid condition is reached.
>
> This thread https://lkml.org/lkml/2018/5/10/773 will give you all the answers
> you are looking for (well very likely).
>
> Let me know if it helped.

In our case , Delta: 174760 ns

1530553351:205762284
1530553351:205762404
--------------------
1530553351:205951226
1530553351:205776466
--------------------

I have tried the workaround for ARM64_ERRATUM_858921, that also fixes the issue.

But all the workaround disables ARM64 VDSO. How do we conclude that is it VDSO issue or ARM64_ERRATUM issue?

Please share your ideas.

Regards,
Biju

> > timer {
> >                 compatible = "arm,armv8-timer";
> >                 interrupts-extended = <&gic GIC_PPI 13
> (GIC_CPU_MASK_SIMPLE(6) | IRQ_TYPE_LEVEL_LOW)>,
> >                                       <&gic GIC_PPI 14 (GIC_CPU_MASK_SIMPLE(6) |
> IRQ_TYPE_LEVEL_LOW)>,
> >                                       <&gic GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(6) |
> IRQ_TYPE_LEVEL_LOW)>,
> >                                       <&gic GIC_PPI 10
> > (GIC_CPU_MASK_SIMPLE(6) | IRQ_TYPE_LEVEL_LOW)>;
> > +                fsl,erratum-a008585;
> > }
>
>
>
>
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