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

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

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.

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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