[PATCH 1/1] ARM: dts: imx6qdl.dtsi: add "arm, shared-override" for pl310

[l.stach@pengutronix.de (Lucas Stach)]

Am Montag, den 13.06.2016, 09:42 +0000 schrieb Peter Chen:
>  
> >Am Samstag, den 11.06.2016, 19:57 +0800 schrieb Shawn Guo:
> >> + Lucas
> >>
> >> On Tue, Jun 07, 2016 at 05:39:25PM +0800, Peter Chen wrote:
> >> > The imx6 SMP system has the same DMA memory coherency issue [1] with
> >> > pl310 L2 controller. With this shared override bit set, the customer
> >> > reports the DMA coherency issue is gone. Besides, I have tested the
> >> > performance using USB ethernet with/without this bit, it shows no
> >> > difference.
> >> >
> >> > [1] http://patchwork.ozlabs.org/patch/469362/
> >> >
> >> > Signed-off-by: Peter Chen <peter.chen@nxp.com>
> >> > ---
> >> >  arch/arm/boot/dts/imx6qdl.dtsi | 1 +
> >> >  1 file changed, 1 insertion(+)
> >> >
> >> > diff --git a/arch/arm/boot/dts/imx6qdl.dtsi
> >> > b/arch/arm/boot/dts/imx6qdl.dtsi index ed613eb..30e21ee 100644
> >> > --- a/arch/arm/boot/dts/imx6qdl.dtsi
> >> > +++ b/arch/arm/boot/dts/imx6qdl.dtsi
> >> > @@ -185,6 +185,7 @@
> >> >  			cache-level = <2>;
> >> >  			arm,tag-latency = <4 2 3>;
> >> >  			arm,data-latency = <4 2 3>;
> >> > +			arm,shared-override;
> >>
> >> Lucas had an objection to the change [1], considering the case that
> >> kernel is booted as non-secure.
> >
> >My objection to this change still stands. Configuring the L2C to be compliant to the
> >ARMv7 ARM is at the same level as the CPU workarounds that can not be applied in
> >secure mode. Those must be done in the firmware, if your firmware doesn't do it it's
> >plain broken.
> >
> 
> Sorry, I not understand what's your mean. We only changes L2 configuration when the
> cache is disabled, what problem will be?
> 
If the kernel is booted in non-secure mode, the L2 cache configuration
register is RO and the kernel will crash on the attempt to write into
this register.

Regards,
Lucas