On 3/25/22 17:56, Rolf Eike Beer wrote:
> Am Freitag, 25. März 2022, 15:38:32 CET schrieb Helge Deller:
>> Let the PDC firmware put the CPU into firmware idle loop with
>> pdc_cpu_rendezvous() function.
>>
>> Signed-off-by: Helge Deller <deller@xxxxxx>
>> ---
>> arch/parisc/kernel/process.c | 33 ++++++++++++++++++++++++++++++---
>> 1 file changed, 30 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
>> index ea3d83b6fb62..44fa89fbb280 100644
>> --- a/arch/parisc/kernel/process.c
>> +++ b/arch/parisc/kernel/process.c
>> @@ -38,6 +38,7 @@
>> #include <linux/rcupdate.h>
>> #include <linux/random.h>
>> #include <linux/nmi.h>
>> +#include <linux/sched/hotplug.h>
>>
>> #include <asm/io.h>
>> #include <asm/asm-offsets.h>
>> @@ -46,6 +47,7 @@
>> #include <asm/pdc_chassis.h>
>> #include <asm/unwind.h>
>> #include <asm/sections.h>
>> +#include <asm/cacheflush.h>
>>
>> #define COMMAND_GLOBAL F_EXTEND(0xfffe0030)
>> #define CMD_RESET 5 /* reset any module */
>> @@ -158,10 +160,35 @@ void release_thread(struct task_struct *dead_task)
>> int running_on_qemu __ro_after_init;
>> EXPORT_SYMBOL(running_on_qemu);
>>
>> -void __cpuidle arch_cpu_idle_dead(void)
>> +/*
>> + * Called from the idle thread for the CPU which has been shutdown.
>> + */
>> +void arch_cpu_idle_dead(void)
>> {
>> - /* nop on real hardware, qemu will offline CPU. */
>> - asm volatile("or %%r31,%%r31,%%r31\n":::);
>> +#ifdef CONFIG_HOTPLUG_CPU
>> + idle_task_exit();
>> +
>> + local_irq_disable();
>> +
>> + /*
>> + * Tell __cpu_die() that this CPU is now safe to dispose of.
>> + */
>> + (void)cpu_report_death();
>> +
>> + /*
>> + * Ensure that the cache lines are written out.
>> + */
>> + flush_cache_all_local();
>> + flush_tlb_all_local(NULL);
>> +
>> + /*
>> + * Let PDC firmware put CPU into firmware idle loop.
>> + */
>> + __pdc_cpu_rendezvous();
>
> That could all be one-line comments for a higher code/line ratio ;)
Yes. The syntax is mostly copied from other arches, where it's like this.
Helge
