[U-Boot] [PATCH v2 12/12] tegra: Set CNTFRQ for secondary CPUs

[Jan Kiszka]

On 2015-02-16 14:51, Mark Rutland wrote:
> On Mon, Feb 16, 2015 at 01:44:36PM +0000, Jan Kiszka wrote:
>> On 2015-02-16 14:37, Mark Rutland wrote:
>>> On Mon, Feb 16, 2015 at 12:54:49PM +0000, Jan Kiszka wrote:
>>>> We only set CNTFRQ in arch_timer_init for the boot CPU. But this has to
>>>> happen for all cores.
>>>>
>>>> Fixing this resolves problems of KVM with emulating the generic
>>>> timer/counter.
>>>>
>>>> Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
>>>> ---
>>>>  arch/arm/cpu/armv7/tegra-common/psci.S | 13 +++++++++++++
>>>>  1 file changed, 13 insertions(+)
>>>>
>>>> diff --git a/arch/arm/cpu/armv7/tegra-common/psci.S b/arch/arm/cpu/armv7/tegra-common/psci.S
>>>> index b7501fb..119c246 100644
>>>> --- a/arch/arm/cpu/armv7/tegra-common/psci.S
>>>> +++ b/arch/arm/cpu/armv7/tegra-common/psci.S
>>>> @@ -51,12 +51,25 @@ ENTRY(psci_arch_init)
>>>>  
>>>>  	mrc	p15, 0, r4, c0, c0, 5	@ MPIDR
>>>>  	and	r4, r4, #7		@ number of CPUs in cluster
>>>> +
>>>> +	adr	r5, _sys_clock_freq
>>>> +	cmp	r4, #0
>>>> +
>>>> +	mrceq   p15, 0, r7, c14, c0, 0	@ read CNTFRQ from CPU0
>>>> +	streq	r7, [r5]
>>>> +
>>>> +	ldrne	r7, [r5]
>>>> +	mcrne   p15, 0, r7, c14, c0, 0	@ write CNTFRQ to CPU1..3
>>>
>>> Is it not possible to have a hook that uses the same variable as
>>> arch_timer_init rather than doing a here copy? It seems a shame to
>>> duplicate the effort.
>>
>> The problem is related to the different address spaces. Here we run in
>> the secure monitor, arch_timer_init - to my understanding - in
>> non-secure mode. Didn't find a pattern so far how to transfer data (and
>> that shouldn't be more complex than the above code).
> 
> Surely arch_timer_init must be run in a secure mode in order to be
> allowed to write to CNTFRQ?

Ah, right.

> 
> If this is simply the easiest way of moving the data around then there's
> no real problem with it; it's just a shame that it only happens in the
> PSCI case.

OK, I'll check again. Maybe it's easier than I thought.

Jan

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