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

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Message-ID: <558D9492.3070008@ti.com>
Date:	Fri, 26 Jun 2015 14:06:10 -0400
From:	Vitaly Andrianov <vitalya@...com>
To:	Grygorii Strashko <grygorii.strashko@...com>,
	santosh shilimkar <santosh.shilimkar@...cle.com>,
	Mark Rutland <mark.rutland@....com>
CC:	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"ssantosh@...nel.org" <ssantosh@...nel.org>
Subject: Re: [PATCH] keystone: psci: adds cpu_die implementation



On 06/26/2015 01:47 PM, Grygorii Strashko wrote:
> Hi,
>
> On 06/26/2015 07:57 PM, Vitaly Andrianov wrote:
>> On 06/25/2015 02:42 PM, santosh shilimkar wrote:
>>> On 6/25/2015 10:20 AM, Mark Rutland wrote:
>>>>>> I need rework and re-test the patch.
>>>>>> One more question. Shall I post the dts related commit, which add PSCI
>>>>>> command together with this commit? Or it may be posted later
>>>>>> independently?
>>>>>
>>>>> The DTS and Kconfig changes can be seaprate patches, but they'll
>>>>> need to
>>>>> go through at the same time.
>>>>
>>>> If your bootloader patches the DTB then you don't even need a dts
>>>> update. That should make things less confusing for existing users...
>>>>
>>> More than confusing we need to keep existing DTB binding work with
>>> updated kernel at least for as basic as booting all the CPUs.
>>>
>>> Regards,
>>> Santosh
>>>
>>>
>> OK. Now I'm confused :) We may have several different configurations here:
>>
>> 1) CONFIG_HOTPLUG_CPU and CONFIG_ARM_PSCI are not set.
>>      In this case keystone arch needs to have
>>      keystone_smp_boot_secondary();
>>
>> 2) CONFIG_HOTPLUG_CPU=y and CONFIG_ARM_PSCI is not set.
>>      keystone_smp_boot_secondary() is required and non PSCI
>>      implementation of keystone_cpu_die() is also required.
>>
>> 3) CONFIG_HOTPLUG_CPU is not set and CONFIG_ARM_PSCI=y
>> 4) CONFIG_HOTPLUG_CPU=y and CONFIG_ARM_PSCI=y
>>
>>      How do I boot secondary CPUs in cases of 3 and 4?
>>      Do I need to implement PSCI version of the
>>      keystone_smp_boot_secondary() of adding PSCI commands to DTB is
>>      enough?
>>
>>      Do I need to implement keystone_cpu_die() if PSCI commands are
>>      added to DTB?
>
> Things are more or less simple here :)
> 1) to support psci you need to have DT entry like below:
> 	psci {
> 		compatible	= "arm,psci";
> 		method		= "smc";
> 		cpu_off		= <0x84000002>;
> 		cpu_on		= <0x84000003>;
> 	};
> and CONFIG_ARM_PSCI=y
>
> in this case Kernel will ignore mach.smp = smp_ops(keystone_smp_ops),
> and will use PSCU interface (see setup_arch()0
>
> 2) if don't have PSCI DT entry, but still have custom smp_operations -
> they will be used.
>
> So, question here is not about   CONFIG_HOTPLUG_CPU, but rather
> will you support "PSCI only" or "PSCI and legacy boot".
>
> For the last case You should keep mach specific code in mach-kestone/platsmp.c.
> For the first case "PSCI only" - above code can be removed.
>
> 3) if you'd like CONFIG_HOTPLUG_CPU in legacy mode - platsmp.c can be updated as below,
> without using psci:
>
>
> +#define KEYSTONE_MON_CPU_DOWN_IDX              0x01
> +#ifdef CONFIG_HOTPLUG_CPU
> +static void __ref keystone_smp_cpu_die(unsigned int cpu)
> +{
> +       int error;
> +
> +       error = keystone_cpu_smc(KEYSTONE_MON_CPU_DOWN_IDX, cpu, 0);
> +       if (error)
> +               pr_err("CPU %u->%u down failed with %d\n",
> +                      smp_processor_id(), cpu, error);
> +
> +       cpu_do_idle();
> +}
> +#endif
>
> Another question is how well current PSCI implementation supports keystone2/LPAE !?
>
That is exactly what I'm working on now :)

> - It seems, at least below hack should be applied :(
>
> +++ b/arch/arm/kernel/psci_smp.c
> @@ -51,7 +51,7 @@ static int psci_boot_secondary(unsigned int cpu, struct task_struct *idle)
>   {
>          if (psci_ops.cpu_on)
>                  return psci_ops.cpu_on(cpu_logical_map(cpu),
> -                                      __pa(secondary_startup));
> +                                       virt_to_idmap(&secondary_startup));
>          return -ENODEV;
>   }
>
> - and what to do with code in keystone_smp_secondary_initmem() ?:
>
> static void __cpuinit keystone_smp_secondary_initmem(unsigned int cpu)
> {
> 	pgd_t *pgd0 = pgd_offset_k(0);
> 	cpu_set_ttbr(1, __pa(pgd0) + TTBR1_OFFSET);
> 	local_flush_tlb_all();
> }
>
>

Thanks,
Vitaly
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