[PATCH] msm: timer: compensate for timer shift in msm_read_timer_count

[PATCH] msm: timer: compensate for timer shift in msm_read_timer_count

[Jeff Ohlstein]

Some msm targets have timers whose lower bits are unreliable. So, we
present our timers as lower frequency than they actually are, and ignore
the bottom 5 bits on such targets. This compensation was erroneously
removed from the msm_read_timer_count function, so restore it.

This was broken by 94790ec25 "msm: timer: SMP timer support for msm".

Change-Id: I8c56bdf82629638748ccf352118ea664f967b87d
Signed-off-by: Jeff Ohlstein <johlstei@codeaurora.org>
---
 arch/arm/mach-msm/timer.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mach-msm/timer.c b/arch/arm/mach-msm/timer.c
index 38b95e9..b3579fe 100644
--- a/arch/arm/mach-msm/timer.c
+++ b/arch/arm/mach-msm/timer.c
@@ -100,7 +100,7 @@ static cycle_t msm_read_timer_count(struct clocksource *cs)
 {
 	struct msm_clock *clk = container_of(cs, struct msm_clock, clocksource);
 
-	return readl(clk->global_counter);
+	return readl(clk->global_counter) >> clk->shift;
 }
 
 static struct msm_clock *clockevent_to_clock(struct clock_event_device *evt)
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

Re: [PATCH] msm: timer: compensate for timer shift in msm_read_timer_count

[Daniel Walker]

On Wed, 2011-06-08 at 20:44 -0700, Jeff Ohlstein wrote:
> Some msm targets have timers whose lower bits are unreliable. So, we
> present our timers as lower frequency than they actually are, and ignore
> the bottom 5 bits on such targets. This compensation was erroneously
> removed from the msm_read_timer_count function, so restore it.
> 
> This was broken by 94790ec25 "msm: timer: SMP timer support for msm".
> 
> Change-Id: I8c56bdf82629638748ccf352118ea664f967b87d

Drop this Change-ID ..

> Signed-off-by: Jeff Ohlstein <johlstei@codeaurora.org>
> ---
>  arch/arm/mach-msm/timer.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/mach-msm/timer.c b/arch/arm/mach-msm/timer.c
> index 38b95e9..b3579fe 100644
> --- a/arch/arm/mach-msm/timer.c
> +++ b/arch/arm/mach-msm/timer.c
> @@ -100,7 +100,7 @@ static cycle_t msm_read_timer_count(struct clocksource *cs)
>  {
>  	struct msm_clock *clk = container_of(cs, struct msm_clock, clocksource);
>  
> -	return readl(clk->global_counter);
> +	return readl(clk->global_counter) >> clk->shift;
>  }

Could you comment in the code with something explaining what the shift
is doing.

Daniel

Re: [PATCH] msm: timer: compensate for timer shift in msm_read_timer_count

[David Brown]

On Thu, Jun 09 2011, Daniel Walker wrote:

>> diff --git a/arch/arm/mach-msm/timer.c b/arch/arm/mach-msm/timer.c
>> index 38b95e9..b3579fe 100644
>> --- a/arch/arm/mach-msm/timer.c
>> +++ b/arch/arm/mach-msm/timer.c
>> @@ -100,7 +100,7 @@ static cycle_t msm_read_timer_count(struct clocksource *cs)
>>  {
>>  	struct msm_clock *clk = container_of(cs, struct msm_clock, clocksource);
>>  
>> -	return readl(clk->global_counter);
>> +	return readl(clk->global_counter) >> clk->shift;
>>  }
>
> Could you comment in the code with something explaining what the shift
> is doing.

Probably best to describe this near msm_clock's definition (or
MSM_DGT_SHIFT), since it is a bit unclear what these values are.
A good (but short) description of how the shifts and even why.

The comment shouldn't be in the function body (CodingStyle, chapter 8).

David

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.