linux-kernel - Re: [PATCH] ARM: arch timer: Set the TVAL before timer is enabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Mon, 24 Jun 2013 10:10:31 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Rohit Vaswani <rvaswani@...eaurora.org>
CC:	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Russell King <linux@....linux.org.uk>,
	Stephen Boyd <sboyd@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: arch timer: Set the TVAL before timer is enabled

On 21/06/13 21:31, Rohit Vaswani wrote:
> On some hardware, the timer deasserts the interrupt when a
> new TVAL is written only when the enable bit is cleared.
> Hence explicitly disable the timer and then program the
> TVAL followed by enabling the timer.
> If this order is not followed, there are chances that
> you would not receive any timer interrupts.
> This is done as suggested in https://lkml.org/lkml/2012/8/11/39
> 
> Signed-off-by: Rohit Vaswani <rvaswani@...eaurora.org>
> ---
>  drivers/clocksource/arm_arch_timer.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index a2b2541..05ba0c2 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -103,9 +103,10 @@ static inline void set_next_event(const int access, unsigned long evt)
>  {
>  	unsigned long ctrl;
>  	ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL);
> -	ctrl |= ARCH_TIMER_CTRL_ENABLE;
> -	ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;
> +	ctrl &= ~(ARCH_TIMER_CTRL_ENABLE | ARCH_TIMER_CTRL_IT_MASK);
> +	arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl);
>  	arch_timer_reg_write(access, ARCH_TIMER_REG_TVAL, evt);
> +	ctrl |= ARCH_TIMER_CTRL_ENABLE;
>  	arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl);
>  }

Maybe that would deserve a comment in the code so people don't get the
idea it can be reordered to save the extra write?

Other than that, and FWIW:
Acked-by: Marc Zyngier <marc.zyngier@....com>

	M.
-- 
Jazz is not dead. It just smells funny...

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/