Hi Marc,
Thank you for the review!
On Tue, 20 Feb 2018 18:07:54 +0000
Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> Hi Mylène,
>
> On 19/02/18 08:18, Mylène Josserand wrote:
> > The ARM architected timers use an offset between their physical and
> > virtual counters. That offset should be configured by the bootloader
> > in CNTVOFF.
> >
> > However, the A83t bootloader fails to do so, and we end up with an
> > undefined offset (which in our case is random), meaning that each CPU
> > will have a different time, which isn't working very well.
> >
> > Fix that by setting the arm,cpu-registers-not-fw-configured that will
> > make Linux use the physical timers instead of the virtual ones. One
> > possible side effect would be that the virtualization features would
> > be disabled. However, due to the way the GIC has been integrated in
> > the system, it is already unusable so we're effectively not losing any
> > feature.
> >
> > Signed-off-by: Mylène Josserand <mylene.josserand@xxxxxxxxxxx>
> > ---
> > arch/arm/boot/dts/sun8i-a83t.dtsi | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm/boot/dts/sun8i-a83t.dtsi b/arch/arm/boot/dts/sun8i-a83t.dtsi
> > index e97a6d17b8d0..b9bdb891cf2f 100644
> > --- a/arch/arm/boot/dts/sun8i-a83t.dtsi
> > +++ b/arch/arm/boot/dts/sun8i-a83t.dtsi
> > @@ -123,6 +123,7 @@
> > <GIC_PPI 14 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>,
> > <GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>,
> > <GIC_PPI 10 (GIC_CPU_MASK_SIMPLE(8) | IRQ_TYPE_LEVEL_LOW)>;
> > + arm,cpu-registers-not-fw-configured;
> > };
> >
> > clocks {
> >
>
> Is the firmware dropping you in the kernel in secure or non-secure mode?
For sun8i-a83t, the kernel is in secure mode.
>
> If the later, what you have is the only solution. If the former, that
> I'd suggest you adopt what we already have for the Renesas stuff (see
> arch/arm/mach-shmobile/headsmp-apmu.S and commit 3fd45a136ff6).
>
> It would allow you to use the virtual timer as intended.
Okay, thanks for the commit pointed, I will try to adopt what it is done
for Renesas.
Best regards,
--
Mylène Josserand, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com
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