Re: [RFC PATCH 5/5] RISC-V: Support cpu hotplug.

[Atish Patra]

On 8/21/18 12:55 AM, Christoph Hellwig wrote:
> >   	if (!err) {
> > +
> > +#ifdef CONFIG_HOTPLUG_CPU
> > +		arch_send_call_function_single_ipi(cpu);
> > +#endif
>
> Please just provide a stub version of arch_send_call_function_single_ipi
> for the !CONFIG_HOTPLUG_CPU case instead of the ifdef here.

Done.

> > +#ifdef CONFIG_HOTPLUG_CPU
> > +int can_hotplug_cpu(void)
>
> This should be a bool.
>
> > +{
> > +	if (cpu_ops.cpu_die)
> > +		return 1;
> > +	else
> > +		return 0;
> > +}
>
> 	return cpu_ops.cpu_die != NULL;
>
> > +void default_cpu_die(unsigned int cpu)
> > +{
> > +	int sipval, sieval, scauseval;
> > +
> > +	/* clear all pending flags */
> > +	csr_write(sip, 0);
> > +	/* clear any previous scause data */
> > +	csr_write(scause, 0);
> > +
> > +	do {
> > +		wait_for_interrupt();
> > +		sipval = csr_read(sip);
> > +		sieval = csr_read(sie);
> > +		scauseval = csr_read(scause);
> > +	/* only break if wfi returns for an enabled interrupt */
> > +	} while ((sipval & sieval) == 0 &&
> > +		 scauseval != INTERRUPT_CAUSE_SOFTWARE);
> > +
> > +	boot_sec_cpu();
> > +}
>
> I suspect all of this except for the boot_sec_cpu() should go into
> a helper in irq.c.  

ok. I will try that. That will also solve interrupt cause declarations 
issue. So I can drop patch 4.

Also as-is this probably doesn't work as scauseval
> will have INTERRUPT_CAUSE_FLAG set, making the comparism never true.

Oops. Thanks for catching that. scauseval is declared as int which made 
this code to work. Fixed it.


Regards,
Atish