[U-Boot] [PATCH] armv8: Enable CPUECTLR.SMPEN for data coherency

[Mingkai Hu]

> -----Original Message-----
> From: Prabhakar Kushwaha
> Sent: Friday, July 01, 2016 7:55 AM
> To: york sun; Qianyu Gong; albert.u.boot at aribaud.net; u-boot at lists.denx.de;
> s.temerkhanov at gmail.com; yamada.masahiro at socionext.com
> Cc: Mingkai Hu
> Subject: RE: [U-Boot] [PATCH] armv8: Enable CPUECTLR.SMPEN for data coherency
> 
> Hi York,
> 
> 
> > -----Original Message-----
> > From: U-Boot [mailto:u-boot-bounces at lists.denx.de] On Behalf Of york
> > sun
> > Sent: Thursday, June 30, 2016 10:32 PM
> > To: Qianyu Gong <qianyu.gong at nxp.com>; albert.u.boot at aribaud.net; u-
> > boot at lists.denx.de; s.temerkhanov at gmail.com;
> > yamada.masahiro at socionext.com
> > Cc: Mingkai Hu <mingkai.hu at nxp.com>
> > Subject: Re: [U-Boot] [PATCH] armv8: Enable CPUECTLR.SMPEN for data
> > coherency
> >
> > On 06/30/2016 02:03 AM, Gong Qianyu wrote:
> > > From: Mingkai Hu <mingkai.hu at nxp.com>
> > >
> > > Data coherency is enabled only when the CPUECTLR.SMPEN bit is set.
> > > The SMPEN bit should be set before enabling the data cache.
> > > If not enabled, the cache is not coherent with other cores and data
> > > corruption could occur.
> > >
> > > Signed-off-by: Mingkai Hu <mingkai.hu at nxp.com>
> > > Signed-off-by: Gong Qianyu <Qianyu.Gong at nxp.com>
> > >
> > > diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
> > > index 670e323..735dd67 100644
> > > --- a/arch/arm/cpu/armv8/start.S
> > > +++ b/arch/arm/cpu/armv8/start.S
> > > @@ -81,6 +81,11 @@ reset:
> > >   	msr	cpacr_el1, x0			/* Enable FP/SIMD */
> > >   0:
> > >
> > > +	/* Enalbe SMPEN bit */
> > > +	mrs     x0, S3_1_c15_c2_1               /* cpuactlr_el1 */
> > > +	orr     x0, x0, #0x40
> > > +	msr     S3_1_c15_c2_1, x0
> > > +
> > >   	/* Apply ARM core specific erratas */
> > >   	bl	apply_core_errata
> > >
> > >
> >
> > Qianyu,
> >
> > I wonder what impact this patch has. Did you find it effective on A53 core?
> > According to ARM documents, A57 and A72 seem don't care this bit.
> > Quote
> >
> 
> I have seen big difference on LS1012A with A53 cores after enabling this bit.
> If I don't enable this bit many IPs like SATA, SDHC show coherency issue.
> 

Hi York,

This bit is used to enable hardware management of data coherency with other cores in the cluster
for A53.

"Data coherency is enabled only when the CPUECTLR.SMPEN bit is set. You must set the
SMPEN bit before enabling the data cache. If you do not, then the cache is not coherent with
other cores and data corruption could occur.
"

For A57/A72, this bit enables the processor to receive instruction cache and TLB maintenance
operations broadcast from other processors in the cluster.

We will change the commit message and integrate Mark's comments to guard this setting for
relevant CPUs.

Thanks,
Mingkai