linux-kernel - Re: [PATCH v4 1/5] ARM/ARM64: arch_timer: add macros for bits in control register

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Date:	Tue, 27 Aug 2013 12:37:38 +0100
From:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Will Deacon <Will.Deacon@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v4 1/5] ARM/ARM64: arch_timer: add macros for bits in
 control register

On 27/08/13 12:21, Catalin Marinas wrote:
> On Fri, Aug 23, 2013 at 05:19:05PM +0100, Sudeep KarkadaNagesha wrote:
>> From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
>>
>> Add macros to describe the bitfields in the ARM architected timer
>> control register to make code easy to understand.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>> Reviewed-by: Will Deacon <will.deacon@....com>
>> Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
>> ---
>>  arch/arm/include/asm/arch_timer.h    |  9 +++++++--
>>  arch/arm64/include/asm/arch_timer.h  | 12 ++++++++----
>>  include/clocksource/arm_arch_timer.h |  8 ++++++++
>>  3 files changed, 23 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
>> index e406d57..9ef74da 100644
>> --- a/arch/arm/include/asm/arch_timer.h
>> +++ b/arch/arm/include/asm/arch_timer.h
>> @@ -95,8 +95,13 @@ static inline void arch_counter_set_user_access(void)
>>  
>>  	asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl));
>>  
>> -	/* disable user access to everything */
>> -	cntkctl &= ~((3 << 8) | (7 << 0));
>> +	/* Disable user access to both physical/virtual counters/timers. */
>> +	/* Also disable virtual event stream */
>> +	cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN
>> +			| ARCH_TIMER_USR_VT_ACCESS_EN
>> +			| ARCH_TIMER_VIRT_EVT_EN
>> +			| ARCH_TIMER_USR_VCT_ACCESS_EN
>> +			| ARCH_TIMER_USR_PCT_ACCESS_EN);
>>  
>>  	asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
>>  }
>> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
>> index 98abd47..00b09d0 100644
>> --- a/arch/arm64/include/asm/arch_timer.h
>> +++ b/arch/arm64/include/asm/arch_timer.h
>> @@ -101,12 +101,16 @@ static inline void arch_counter_set_user_access(void)
>>  {
>>  	u32 cntkctl;
>>  
>> -	/* Disable user access to the timers and the physical counter. */
>>  	asm volatile("mrs	%0, cntkctl_el1" : "=r" (cntkctl));
>> -	cntkctl &= ~((3 << 8) | (1 << 0));
>>  
>> -	/* Enable user access to the virtual counter and frequency. */
>> -	cntkctl |= (1 << 1);
>> +	/* Disable user access to the timers and the physical counter. */
>> +	cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN
>> +			| ARCH_TIMER_USR_VT_ACCESS_EN
>> +			| ARCH_TIMER_USR_PCT_ACCESS_EN);
>> +
>> +	/* Enable user access to the virtual counter. */
>> +	cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN;
>> +
>>  	asm volatile("msr	cntkctl_el1, %0" : : "r" (cntkctl));
> 
> For consistency with arm, I think we should also disable the event
> stream explicitly here.
> 
Yes it's done. In PATCH 3/5, a new function arch_timer_evtstrm_config is
added which is always called(PATCH 4/5). It's either enabled or disabled
explicitly based on config option for event stream.

Let me know if you think that's not sufficient.

Regards,
Sudeep

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