Re: [PATCH 2/2] MIPS: CPS: Copy EVA configuration when starting secondary VPs.

[Matt Redfearn]

On 18/05/16 16:04, Paul Burton wrote:
> On Wed, May 18, 2016 at 03:45:22PM +0100, Matt Redfearn wrote:
> > When starting secondary VPEs which support EVA and the SegCtl registers,
> > copy the memory segmentation configuration from the running VPE to ensure
> > that all VPEs in the core have a consitent virtual memory map.
> >
> > The EVA configuration of secondary cores is dealt with when starting the
> > core via the CM.
> >
> > Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxxxx>
> > ---
> >
> >   arch/mips/kernel/cps-vec.S | 16 ++++++++++++++++
> >   1 file changed, 16 insertions(+)
> >
> > diff --git a/arch/mips/kernel/cps-vec.S b/arch/mips/kernel/cps-vec.S
> > index ac81edd44563..07b3274c8ae1 100644
> > --- a/arch/mips/kernel/cps-vec.S
> > +++ b/arch/mips/kernel/cps-vec.S
> > @@ -431,6 +431,22 @@ LEAF(mips_cps_boot_vpes)
> >   	mfc0	t0, CP0_CONFIG
> >   	mttc0	t0, CP0_CONFIG
> >   
> > +	/* Copy the EVA config from this VPE if the CPU supports it */
> > +	mfc0	t0, CP0_CONFIG, 1
> > +	bgez	t0, 1f
> > +	 mfc0	t0, CP0_CONFIG, 2
> > +	bgez	t0, 1f
> > +	 mfc0	t0, CP0_CONFIG, 3
> > +	and	t0, t0, MIPS_CONF3_SC
> > +	beqz	t0, 1f
> > +	 nop
> Hi Matt,
>
> The checks here aren't *quite* right since they do the mfc0 of the next
> register in the delay slot which will happen even if the M bit of the
> preceeding register wasn't set. There are other cases in cps-vec.S where
> I've made that mistake... Luckily, in this particular case, we know that
> we have MT ASE support which means we know that Config3 exists. So I
> think you can just remove the checks of Config1.M & Config2.M and just
> read Config3 straight away.
Good point - thanks Paul :-)

Matt
> Thanks,
>      Paul
>
> > +	mfc0    t0, CP0_SEGCTL0
> > +	mttc0	t0, CP0_SEGCTL0
> > +	mfc0    t0, CP0_SEGCTL1
> > +	mttc0	t0, CP0_SEGCTL1
> > +	mfc0    t0, CP0_SEGCTL2
> > +	mttc0	t0, CP0_SEGCTL2
> > +1:
> >   	/* Ensure no software interrupts are pending */
> >   	mttc0	zero, CP0_CAUSE
> >   	mttc0	zero, CP0_STATUS
> > --
> > 2.5.0