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Subject: Re: [RFC PATCH 5/5] RISC-V: Support cpu hotplug.
To:     Christoph Hellwig <hch@infradead.org>
Cc:     "palmer@sifive.com" <palmer@sifive.com>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "anup@brainfault.org" <anup@brainfault.org>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        Damien Le Moal <Damien.LeMoal@wdc.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <1534377377-70108-1-git-send-email-atish.patra@wdc.com>
 <1534377377-70108-6-git-send-email-atish.patra@wdc.com>
 <20180821075452.GC28079@infradead.org>
From:   Atish Patra <atish.patra@wdc.com>
Message-ID: <2f9a09fa-a334-1910-843b-067537960c24@wdc.com>
Date:   Tue, 21 Aug 2018 13:23:18 -0700
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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