linux-kernel - Re: [PATCH] keystone: psci: adds cpu

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Date:	Thu, 25 Jun 2015 07:59:27 -0700
From:	santosh shilimkar <santosh.shilimkar@...cle.com>
To:	Mark Rutland <mark.rutland@....com>,
	Vitaly Andrianov <vitalya@...com>
Cc:	"ssantosh@...nel.org" <ssantosh@...nel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	lorenzo.pieralisi@....com
Subject: Re: [PATCH] keystone: psci: adds cpu_die implementation

On 6/25/2015 7:45 AM, Mark Rutland wrote:
> Hi,
>
> On Thu, Jun 25, 2015 at 03:02:50PM +0100, Vitaly Andrianov wrote:
>> This commit add cpu_die implementation using psci api
>
> I don't understand. If you have a PSCI implementation, it should be
> sufficient to have a PSCI node (and enable-method) in your DT, and the
> generic code will be used. Nothing should be required in your board
> code.
>
> You should also use CPU_ON to bring secondaries online rather than
> mixing up PSCI and platform-specific mechanisms.
>
Good point about CPU_ON. We need that as well.

>>
>> Signed-off-by: Vitaly Andrianov <vitalya@...com>
>> ---
>>   arch/arm/mach-keystone/platsmp.c | 32 ++++++++++++++++++++++++++++++++
>>   1 file changed, 32 insertions(+)
>>
>> diff --git a/arch/arm/mach-keystone/platsmp.c b/arch/arm/mach-keystone/platsmp.c
>> index 5f46a7c..2c40cc0 100644
>> --- a/arch/arm/mach-keystone/platsmp.c
>> +++ b/arch/arm/mach-keystone/platsmp.c
>> @@ -20,6 +20,7 @@
>>   #include <asm/prom.h>
>>   #include <asm/tlbflush.h>
>>   #include <asm/pgtable.h>
>> +#include <asm/psci.h>
>>
>>   #include "keystone.h"
>>
>> @@ -51,7 +52,38 @@ static inline void __cpuinit keystone_smp_secondary_initmem(unsigned int cpu)
>>   {}
>>   #endif
>>
>> +
>> +#ifdef CONFIG_HOTPLUG_CPU
>> +static void keystone_cpu_die(unsigned int cpu)
>> +{
>> +#ifdef CONFIG_ARM_PSCI
>> +	struct psci_power_state pwr_state = {0, 0, 0};
>> +
>> +	pr_info("keystone_cpu_die(%d) from %d using PSCI\n", cpu,
>> +	       smp_processor_id());
>> +
>> +	if (psci_ops.cpu_off)
>> +		psci_ops.cpu_off(pwr_state);
>> +#else
>> +	/*
>> +	 * We may want to add here a direct smc call to monitor
>> +	 * if the kernel doesn't support PSCI API
>> +	 */
>> +#endif
>
> You should determine this from your DT. Your FW/bootloader can patch in
> the relevant nodes and properties when support is present, so the
> presence of such nodes should guarantee that PSCI is available.
>
That will be a nice trick. FW already does some tweaks of dts for
LPAE/non_LPAE tweaks.

Regards,
Santosh
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