[PATCH v4 12/13] cpuidle: mvebu: Add initial CPU idle support for Armada 370/XP SoC

[Gregory CLEMENT]

On 19/02/2014 17:51, Thomas Petazzoni wrote:
> Dear Gregory CLEMENT,
> 
> On Thu, 13 Feb 2014 18:33:35 +0100, Gregory CLEMENT wrote:
> 
>> +config ARM_ARMADA_370_XP_CPUIDLE
>> +	bool "CPU Idle Driver for Armada 370/XP family processors"
> 
> Sorry to bring the naming issue, but it looks like the Armada 38x has a
> PMSU that looks almost identical to the Armada XP PMSU, except that it
> doesn't have the L2 fabric registers (probably because Armada 38x uses
> the PL310 and not the Marvell L2 cache).
> 
> Therefore, should this cpuidle driver be named Armada 370/XP, or
> ARMADA_MVEBU for example?

Well most of the code is related to the coherency and the L2 cache, so
a different L2 cache is a significant difference. The CPU are also different
for example the PJ4B can  use LDREX/STREX without MMU whereas the Cortex A9
can't.

> 
>> +noinline static int armada_370_xp_cpu_suspend(unsigned long deepidle)
> 
> 
> 
>> +{
>> +	armada_370_xp_pmsu_idle_prepare(deepidle);
>> +
>> +	v7_exit_coherency_flush(all);
>> +
>> +	ll_clear_cpu_coherent();
>> +
>> +	dsb();
>> +
>> +	wfi();
>> +
>> +	ll_set_cpu_coherent();
>> +
>> +	asm volatile(
>> +	"mrc	p15, 0, %0, c1, c0, 0 \n\t"
>> +	"tst	%0, #(1 << 2) \n\t"
>> +	"orreq	r0, %0, #(1 << 2) \n\t"
>> +	"mcreq	p15, 0, %0, c1, c0, 0 \n\t"
>> +	"isb	"
>> +	: : "r" (0));
> 
> I believe a little comment on top of this assembly block would be good
> to have, to at least give a quick idea on what's going on.

I am on it, I had the same remark from Lorenzo Pieralisi.

> 
> Also, I'm a bit unsure about your choice of mixing C and assembly here.
> This function is already calling ll_clear_cpu_coherent() and
> ll_set_cpu_coherent() that are assembly functions implement in
> coherency_ll.S. Shouldn't we do the same for this final bit of assembly?

I made several tries when I converted most of the code in C, so I am not
sure but I think that using a C function didn't work here. But as Lorenzo
pointed they were mistakes in this code, so once I will have fixed them, I
will try again.


Thanks,

Gregory


> 
> Thomas
> 


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com