Subject: [PATCH v2] ARM: save/restore diagnostic register on Cortex-A9 suspend/resume

From: [email-masked] (Will Deacon)
Date: Tue, 24 Jun 2014 17:33:20 +0100

On Tue, Jun 24, 2014 at 05:28:54PM +0100, Tomasz Figa wrote:
> Hi Shawn,
> 
> On 22.06.2014 12:15, Shawn Guo wrote:
> > The CP15 diagnostic register holds ARM errata bits on Cortex-A9, so it
> > needs to be saved/restored on suspend/resume.  Otherwise, the
> > effectiveness of errata workaround gets lost together with diagnostic
> > register bit across suspend/resume cycle.
> > 
> > The patch adds a couple of Cortex-A9 specific suspend and resume
> > functions to handle the diagnostic register across suspend/resume cycle.
> 
> [snip]
> 
> > +ENTRY(cpu_ca9mp_do_resume)
> > +	ldmia	r0!, {r4}
> > +	mcr	p15, 0, r4, c15, c0, 1  @ Diagnostic register
> 
> What about platforms running in non-secure mode in which the register is
> read-only?

On A9, it should be write-ignore. Are you seeing problems on a real SoC?

Will