[U-Boot] [PATCH v4 02/14] ARM: Factor out armv7_get_cpu_id macro

[Jan Kiszka]

On 2015-02-28 14:56, Marc Zyngier wrote:
> On Fri, 27 Feb 2015 13:28:01 +0000
> Jan Kiszka <jan.kiszka at siemens.com> wrote:
> 
>> Handy for obtaining the ID of the current CPU. We will have more use
>> cases.
>>
>> CC: Marc Zyngier <marc.zyngier at arm.com>
>> Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
>> ---
>>  arch/arm/cpu/armv7/sunxi/psci.S | 4 ++--
>>  arch/arm/include/asm/macro.h    | 7 +++++++
>>  2 files changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/cpu/armv7/sunxi/psci.S
>> b/arch/arm/cpu/armv7/sunxi/psci.S index 9e898f2..0523217 100644
>> --- a/arch/arm/cpu/armv7/sunxi/psci.S
>> +++ b/arch/arm/cpu/armv7/sunxi/psci.S
>> @@ -19,6 +19,7 @@
>>  
>>  #include <config.h>
>>  #include <asm/gic.h>
>> +#include <asm/macro.h>
>>  #include <asm/psci.h>
>>  #include <asm/arch/cpu.h>
>>  
>> @@ -315,8 +316,7 @@ psci_arch_init:
>>  	mcr	p15, 0, r5, c1, c1, 0	@ Write SCR
>>  	isb
>>  
>> -	mrc	p15, 0, r4, c0, c0, 5	@ MPIDR
>> -	and	r4, r4, #3		@ cpu number in cluster
>> +	armv7_get_cpu_id r4
>>  	mov	r5, #0x400		@ 1kB of stack per CPU
>>  	mul	r4, r4, r5
>>  
>> diff --git a/arch/arm/include/asm/macro.h
>> b/arch/arm/include/asm/macro.h index 1c8c425..0bc925a 100644
>> --- a/arch/arm/include/asm/macro.h
>> +++ b/arch/arm/include/asm/macro.h
>> @@ -198,6 +198,13 @@ lr	.req	x30
>>  .endm
>>  #endif
>>  
>> +#else /* !CONFIG_ARM64 */
>> +
>> +.macro armv7_get_cpu_id rn
>> +	mrc	p15, 0, \rn, c0, c0, 5	/* read MPIDR */
>> +	and	\rn, \rn, #0xff		/* return CPU ID
>> in cluster */
>> +.endm
>> +
> 
> How does this work in a multi-cluster situation? Or when you have
> sparse MPIDRs?

I have no idea. That masking was stolen from your code.

The model we assume for PSCI is that there is no cluster and that we
have enough per-cpu space for up to the maximum cpu ID obtained that way.

If you are concerned about signaling a false general applicability of
that macro, I can fold it back into the callers or add some comments
about restrictions. My plan was just to make the caller site a bit more
readable.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux