Re: [PATCH 5/6] [CPUFREQ] S5PV210: Adjust udelay prior to voltage scaling down

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On Wed, Jun 22, 2011 at 05:07:44PM +0900, Kukjin Kim wrote:
> From: Todd Poynor <toddpoynor@xxxxxxxxxx>
> 
> Voltage scaling accesses the MAX8998 regulators over bit-banged I2C
> with lots of udelays.  In the case of decreasing CPU speed, the
> number of loops per us for udelay needs to be adjusted prior to
> decreasing voltage to avoid delaying for up to 10X too long.

This changelog is very specific to a particular board but actually it's
not at all board specific - we should watch out for this with other
cpufreq drivers as I bet there's more with the same issue.  The S3C64xx
driver is affected for example, I'll send a patch shortly.

> 
> Signed-off-by: Todd Poynor <toddpoynor@xxxxxxxxxx>
> Signed-off-by: Jonghwan Choi <jhbird.choi@xxxxxxxxxxx>
> Signed-off-by: Kukjin Kim <kgene.kim@xxxxxxxxxxx>
> ---
>  drivers/cpufreq/s5pv210-cpufreq.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/cpufreq/s5pv210-cpufreq.c b/drivers/cpufreq/s5pv210-cpufreq.c
> index e9b9b7f..78c88a0 100644
> --- a/drivers/cpufreq/s5pv210-cpufreq.c
> +++ b/drivers/cpufreq/s5pv210-cpufreq.c
> @@ -471,6 +471,8 @@ static int s5pv210_target(struct cpufreq_policy *policy,
>  		}
>  	}
>  
> +	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
> +
>  	if (freqs.new < freqs.old) {
>  		/* Voltage down: will be implemented */
>  		if (!IS_ERR(arm_regulator) &&
> @@ -483,7 +485,6 @@ static int s5pv210_target(struct cpufreq_policy *policy,
>  		}
>  	}
>  
> -	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
>  
>  	printk(KERN_DEBUG "Perf changed[L%d]\n", index);
>  
> -- 
> 1.7.1
> 
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