linux-kernel - Re: [PATCH linux-next tag: next-20210322] ARM: aspeed: Add CPU hotplug callbacks for kexec support

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Message-ID: <7c8ca40f-3f73-d8ea-08e2-ee7c0b0b6ab1@linux.vnet.ibm.com>
Date:   Mon, 22 Mar 2021 11:07:02 -0700
From:   Bruce Mitchell <bruce.mitchell@...ux.vnet.ibm.com>
To:     Joel Stanley <joel@....id.au>, openbmc@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Andrew Jeffery <andrew@...id.au>,
        Eddie James <eajames@...ux.ibm.com>
Subject: Re: [PATCH linux-next tag: next-20210322] ARM: aspeed: Add CPU
 hotplug callbacks for kexec support

On 3/22/2021 09:40, Bruce Mitchell wrote:
> On 3/22/2021 08:57, Bruce Mitchell wrote:
>> These callbacks are required for kexec to function. The AST2600 does not
>> expose any controls for powering down it's CPU cores, so we borrow the
>> approach taken from socfpga and wait in the idle loop.
>>
>> Author: Joel Stanley <joel@....id.au>
>>
>> Signed-off-by: Bruce Mitchell <bruce.mitchell@...ux.vnet.ibm.com>
>> ---
>>   arch/arm/mach-aspeed/platsmp.c | 20 ++++++++++++++++++++
>>   1 file changed, 20 insertions(+)
>>
>> diff --git a/arch/arm/mach-aspeed/platsmp.c 
>> b/arch/arm/mach-aspeed/platsmp.c
>> index 2324becf7991..1ae3ff5a9701 100644
>> --- a/arch/arm/mach-aspeed/platsmp.c
>> +++ b/arch/arm/mach-aspeed/platsmp.c
>> @@ -7,6 +7,8 @@
>>   #include <linux/of.h>
>>   #include <linux/smp.h>
>>
>> +#include <asm/proc-fns.h>
>> +
>>   #define BOOT_ADDR    0x00
>>   #define BOOT_SIG    0x04
>>
>> @@ -53,9 +55,27 @@ static void __init 
>> aspeed_g6_smp_prepare_cpus(unsigned int max_cpus)
>>       iounmap(base);
>>   }
>>
>> +#ifdef CONFIG_HOTPLUG_CPU
>> +static void aspeed_g6_cpu_die(unsigned int cpu)
>> +{
>> +        /* Do WFI. If we wake up early, go back into WFI */
>> +        while (1)
>> +                cpu_do_idle();
>> +}
>> +
>> +static int aspeed_g6_cpu_kill(unsigned int cpu)
>> +{
>> +        return 1;
>> +}
>> +#endif
>> +
>>   static const struct smp_operations aspeed_smp_ops __initconst = {
>>       .smp_prepare_cpus    = aspeed_g6_smp_prepare_cpus,
>>       .smp_boot_secondary    = aspeed_g6_boot_secondary,
>> +#ifdef CONFIG_HOTPLUG_CPU
>> +    .cpu_die        = aspeed_g6_cpu_die,
>> +    .cpu_kill        = aspeed_g6_cpu_kill,
>> +#endif
>>   };
>>
>>   CPU_METHOD_OF_DECLARE(aspeed_smp, "aspeed,ast2600-smp", 
>> &aspeed_smp_ops);
>>
> 
> Adding Andrew Jeffery and Eddie James to the CC list.
> 

Adding linux-kernel@...r.kernel.org and 
linux-arm-kernel@...ts.infradead.org based feedback.