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Subject: Re: [PATCH V2] ARM: mach-shmobile: Don't init CNTVOFF if PSCI is
 available
To:     Julien Grall <julien.grall@arm.com>,
        linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     horms@verge.net.au, magnus.damm@gmail.com, linux@armlinux.org.uk,
        biju.das@bp.renesas.com,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
References: <1556882268-27451-1-git-send-email-olekstysh@gmail.com>
 <b52a7c3f-6e10-b45e-4cb9-859ac4b468a8@arm.com>
From:   Oleksandr <olekstysh@gmail.com>
Message-ID: <6495fca7-bdfa-9020-4eff-b2d04c19827a@gmail.com>
Date:   Fri, 10 May 2019 15:27:50 +0300
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On 06.05.19 18:37, Julien Grall wrote:
> Hi Oleksandr,

Hi Julien


>> ---
>>   arch/arm/mach-shmobile/setup-rcar-gen2.c | 13 ++++++++++++-
>>   1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-shmobile/setup-rcar-gen2.c 
>> b/arch/arm/mach-shmobile/setup-rcar-gen2.c
>> index eea60b2..bc8537b 100644
>> --- a/arch/arm/mach-shmobile/setup-rcar-gen2.c
>> +++ b/arch/arm/mach-shmobile/setup-rcar-gen2.c
>> @@ -17,7 +17,9 @@
>>   #include <linux/of.h>
>>   #include <linux/of_fdt.h>
>>   #include <linux/of_platform.h>
>> +#include <xen/xen.h>
>>   #include <asm/mach/arch.h>
>> +#include <asm/psci.h>
>>   #include <asm/secure_cntvoff.h>
>>   #include "common.h"
>>   #include "rcar-gen2.h"
>> @@ -63,7 +65,16 @@ void __init rcar_gen2_timer_init(void)
>>       void __iomem *base;
>>       u32 freq;
>>   -    secure_cntvoff_init();
>> +    /*
>> +     * If PSCI is available then most likely we are running on 
>> PSCI-enabled
>> +     * U-Boot which, we assume, has already taken care of resetting 
>> CNTVOFF
>> +     * before switching to non-secure mode and we don't need to.
>> +     * Another check is to be sure that we are not running on top of 
>> Xen
>> +     * hypervisor, as CNTVOFF is controlled by hypervisor itself and
>> +     * shouldn't be touched by Dom0 in such case.
>
> If you are running on top of Xen, then PSCI will be available. So is 
> there any real value to check the presence of Xen as well?

I think, no. If the PSCI is a must to run Xen, then it is certainly an 
excessive check. I will drop it in V3.


>
> Cheers,
>
-- 
Regards,

Oleksandr Tyshchenko