[PATCH v8 04/13] arm64/acpi: Create arch specific cpu to acpi id helper

Jeremy Linton jeremy.linton at arm.com
Thu Apr 26 11:33:14 PDT 2018


On 04/26/2018 05:27 AM, Sudeep Holla wrote:
> On 26/04/18 00:31, Jeremy Linton wrote:
>> Its helpful to be able to lookup the acpi_processor_id associated
>> with a logical cpu. Provide an arm64 helper to do this.
> As I pointed out in the earlier version, this patch is not required.
> The acpi_id stored in the acpi_processor can be used for this.
> Won't the below change make it work ? I can't think of any reason why it
> shouldn't.

So, I only noticed your previous email last night on the mail archive, 
as I was applying your review/ack tags and couldn't find a response for 
this patch, seem the spam/etc filters need some further tweaking!

At that point, I was pretty sure the suggestion wasn't going to work out 
of the box as a lot of this code is running fairly early in the boot 
process. I spent a bit of time and plugged the change in to verify that 
assertion, and yes the per_cpu processor/acpi bits aren't setup early 
enough to be used by much of this code. It is being called from 
init_cpu_topology()/smp_prepare_cpus() which precedes 
do_basic_setup/do_initcalls() which is what runs the acpi_init() 
sequence which ends up eventually allocating the required data 
structures. So without restructuring the core boot sequence, this seems 
like a reasonable solution.


> Regards,
> Sudeep
> -->8
> diff --git i/drivers/acpi/pptt.c w/drivers/acpi/pptt.c
> index 0fc4b2654665..f421f58b4ae6 100644
> --- i/drivers/acpi/pptt.c
> +++ w/drivers/acpi/pptt.c
> @@ -432,7 +432,7 @@ static void cache_setup_acpi_cpu(struct
> acpi_table_header *table,
>   {
>          struct acpi_pptt_cache *found_cache;
>          struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> -       u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> +       u32 acpi_cpu_id = per_cpu(processors, cpu)->acpi_id;
>          struct cacheinfo *this_leaf;
>          unsigned int index = 0;
>          struct acpi_pptt_processor *cpu_node = NULL;

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