linux-kernel - Re: [PATCH] ARM: mach-shmobile: Don't configure ARCH timer if PSCI is enabled

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Date:   Thu, 18 Apr 2019 14:15:51 +0300
From:   Oleksandr <olekstysh@...il.com>
To:     Julien Grall <julien.grall@....com>,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     horms@...ge.net.au, magnus.damm@...il.com, linux@...linux.org.uk,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Subject: Re: [PATCH] ARM: mach-shmobile: Don't configure ARCH timer if PSCI is
 enabled


On 18.04.19 12:32, Julien Grall wrote:
> Hi,

Hi Julien


<snip>

>>
>> diff --git a/arch/arm/mach-shmobile/setup-rcar-gen2.c 
>> b/arch/arm/mach-shmobile/setup-rcar-gen2.c
>> index eea60b2..bac4490 100644
>> --- a/arch/arm/mach-shmobile/setup-rcar-gen2.c
>> +++ b/arch/arm/mach-shmobile/setup-rcar-gen2.c
>> @@ -32,7 +32,7 @@ static const struct of_device_id cpg_matches[] 
>> __initconst = {
>>       { /* sentinel */ }
>>   };
>>   -static unsigned int __init get_extal_freq(void)
>> +static unsigned int __init __maybe_unused get_extal_freq(void)
>>   {
>>       const struct of_device_id *match;
>>       struct device_node *cpg, *extal;
>> @@ -60,6 +60,12 @@ static unsigned int __init get_extal_freq(void)
>>     void __init rcar_gen2_timer_init(void)
>>   {
>> +/*
>> + * If CONFIG_PSCI is enabled then most likely we are running on 
>> PSCI-enabled
>> + * U-Boot which, we assume, has already taken care of configuring 
>> ARCH timer
>> + * stuff before switching to non-secure mode.
>> + */
>
> I disagree with that statement. CONFIG_ARM_PSCI may be selected in 
> your .config for multiple reasons:
>      - CONFIG_XEN will selected it
>      - you build a .config targeting multiple platforms
>
> Yet you may still want to boot the kernel on older U-boot. Such change 
> would make it impossible.
>
> If there are code that should not be called when PSCI is used, then 
> you need to make sure the function is not called at runtime.

I got your point.


As I answered in a previous email:

 > But "#if !defined(CONFIG_ARM_PSCI)" wraps secure_cntvoff_init() call as
 > well, which resets CNTVOFF,

 > and this is something I tried to avoid the first from being executed on
 > a CPU, which is in SVC mode (when running on top of Xen).

What would be a proper way to avoid calling secure_cntvoff_init() at 
runtime?

Check that we are already in non-secure mode and/or cntvoff is already 0?


>
> Cheers,
>
-- 
Regards,

Oleksandr Tyshchenko