[U-Boot] [PATCH] arm: psci: save and restore registers from r4 to r12

[Chenhui Zhao]

On Thu, Oct 13, 2016 at 5:52 PM, Chen-Yu Tsai <wens at csie.org> wrote:
> On Sat, Oct 8, 2016 at 7:08 PM, Chenhui Zhao <chenhui.zhao at nxp.com> wrote:
>> Save and restore core registers from r4 to r12 so that PSCI code won't
>> break their value.
>>
>> Signed-off-by: Chenhui Zhao <chenhui.zhao at nxp.com>
>> Signed-off-by: Alison Wang <alison.wang at nxp.com>
>> Signed-off-by: Abhimanyu Saini <abhimanyu.saini at nxp.com>
>> ---
>>  arch/arm/cpu/armv7/psci.S | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/cpu/armv7/psci.S b/arch/arm/cpu/armv7/psci.S
>> index 6a36208..746297c 100644
>> --- a/arch/arm/cpu/armv7/psci.S
>> +++ b/arch/arm/cpu/armv7/psci.S
>> @@ -152,7 +152,7 @@ _psci_table:
>>         .word   0
>>
>>  _smc_psci:
>> -       push    {r4-r7,lr}
>> +       push    {r4-r12,lr}
>
> This change is not needed. This function only uses r4-r7.
> Any subroutines called should save variable registers (r4-r12)
> themselves, per the ARM calling conventions.
>
> ChenYu
>

I do not think it is a normal calling, instead it is an exception
handler. In the exception context,
it is necessary to save/restore all registers.

Sorry, my mail server has something wrong.

Chenhui

>>
>>         @ Switch to secure
>>         mrc     p15, 0, r7, c1, c1, 0
>> @@ -175,7 +175,7 @@ _smc_psci:
>>         @ Switch back to non-secure
>>  2:     mcr     p15, 0, r7, c1, c1, 0
>>
>> -       pop     {r4-r7, lr}
>> +       pop     {r4-r12, lr}
>>         movs    pc, lr                  @ Return to the kernel
>>
>>  @ Requires dense and single-cluster CPU ID space
>> --
>> 1.9.1
>>
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