[PATCH] ARM: psci: boot_secondary: replace __pa with virt_to_idmap

[vitalya@ti.com (Vitaly Andrianov)]

On 06/30/2015 11:59 AM, Nicolas Pitre wrote:
> On Tue, 30 Jun 2015, Russell King - ARM Linux wrote:
>
>> On Tue, Jun 30, 2015 at 01:44:22PM +0300, Grygorii Strashko wrote:
>>> On some PAE systems (e.g. TI Keystone), memory is above the 32-bit
>>> addressable limit, and the interconnect provides an aliased view of
>>> parts of physical memory in the 32-bit addressable space. This alias
>>> is strictly for boot time usage, and is not otherwise usable because
>>> of coherency limitations.
>>>
>>> On such systems, the idmap mechanism has to be used to pass correct
>>> boot address of secondary CPU to FW.
>>> virt_to_idmap() will fall-back to existing virt_to_phys() macro if
>>> such conversation is not required.
>>
>> I think this could do with improvement so that those who aren't aware of
>> the issue can understand better.  The idmap mechanism is always used for
>> secondary booting anyway.
>>
>> "In this case, virt_to_phys(secondary_startup) would return the
>> physical address of the secondary CPU boot entry point, but on such
>> systems, this would be above the 4GB limit.
>>
>> A separate function, virt_to_idmap(), has been provided to return a
>> usable physical address for functions in the identity mapping, and
>> this must be used in preference to virt_to_phys() or __pa() to find
>> the physical entry point for functions in the identity mapping range.
>>
>> For other systems, virt_to_idmap() and virt_to_phys() return identical
>> physical addresses."
>>
>>>
>>> Cc: Mark Rutland <mark.rutland@arm.com>
>>> Cc: Nicolas Pitre <nico@linaro.org>
>>> Cc: Santosh Shilimkar <ssantosh@kernel.org>
>>> Cc: Vitaly Andrianov <vitalya@ti.com>
>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>
>> Code-wise, this looks correct to me - but as it's PSCI stuff, I'd like
>> to see Nico ack it.
>
> I cannot pretend to be the authority on PSCI stuff.
>
> But this looks correct to me as well, assuming the amended commit
> message.
>
> Acked-by: Nicolas Pitre <nico@linaro.org>
>
>> Thanks.
>>
>>> ---
>>>   arch/arm/kernel/psci_smp.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm/kernel/psci_smp.c b/arch/arm/kernel/psci_smp.c
>>> index 28a1db4..244aadd 100644
>>> --- a/arch/arm/kernel/psci_smp.c
>>> +++ b/arch/arm/kernel/psci_smp.c
>>> @@ -51,7 +51,7 @@ static int psci_boot_secondary(unsigned int cpu, struct task_struct *idle)
>>>   {
>>>   	if (psci_ops.cpu_on)
>>>   		return psci_ops.cpu_on(cpu_logical_map(cpu),
>>> -				       __pa(secondary_startup));
>>> +					virt_to_idmap(&secondary_startup));
>>>   	return -ENODEV;
>>>   }
>>>
>>> --
>>> 2.4.5
>>>
>>
>> --
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>>
>>
Tested-by Vitaly Andrianov <vitalya@ti.com>