[RFC PATCH v2 3/5] ARM: kernel: update cpu_suspend code to use cache LoUIS operations

[Guennadi Liakhovetski]

Hi Will

On Tue, 11 Dec 2012, Will Deacon wrote:

> On Tue, Dec 11, 2012 at 04:33:13PM +0000, Will Deacon wrote:
> > On Tue, Dec 11, 2012 at 04:07:56PM +0000, Guennadi Liakhovetski wrote:
> > > Git bisect identified this patch, in the mainline as
> > > 
> > > commit dbee0c6fb4c1269b2dfc8b0b7a29907ea7fed560
> > > Author: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> > > Date:   Fri Sep 7 11:06:57 2012 +0530
> > > 
> > >     ARM: kernel: update cpu_suspend code to use cache LoUIS operations
> > > 
> > > as the culprit of the broken wake up from STR on mackerel, based on an 
> > > sh7372 A8 SoC. .config attached.
> > 
> > My guess is that because Cortex-A8 does not implement the MP extensions,
> > the LoUIS field of the CLIDR reads as zero, and the cache isn't flushed at
> > all (I can see an early exit in v7_flush_dcache_louis).
> > 
> > Lorenzo -- how is this supposed to work for uniprocessor CPUs?
> 
> Bah, forgot to ask you if the following patch helps...

Yes, it does.

Thanks
Guennadi

> 
> Will
> 
> --->8
> 
> diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
> index cd95664..f58248f 100644
> --- a/arch/arm/mm/cache-v7.S
> +++ b/arch/arm/mm/cache-v7.S
> @@ -44,7 +44,8 @@ ENDPROC(v7_flush_icache_all)
>  ENTRY(v7_flush_dcache_louis)
>         dmb                                     @ ensure ordering with previous memory accesses
>         mrc     p15, 1, r0, c0, c0, 1           @ read clidr, r0 = clidr
> -       ands    r3, r0, #0xe00000               @ extract LoUIS from clidr
> +       ALT_SMP(ands    r3, r0, #(7 << 21))     @ extract LoUIS from clidr
> +       ALT_UP(ands     r3, r0, #(7 << 27))     @ extract LoUU from clidr
>         mov     r3, r3, lsr #20                 @ r3 = LoUIS * 2
>         moveq   pc, lr                          @ return if level == 0
>         mov     r10, #0                         @ r10 (starting level) = 0
> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/