Re: [pm-wip/cpufreq] [PATCH] OMAP2+: CPUfreq: update lpj with reference value to avoid progressive error.

[Kevin Hilman <khilman@ti.com>]

Santosh Shilimkar <santosh.shilimkar@ti.com> writes:

> From: Russell King <rmk+kernel@arm.linux.org.uk>
>
> Adjust _both_ the per-cpu loops_per_jiffy and global lpj. Calibrate them
> with with reference to the initial values to avoid a progressively
> bigger and bigger error in the value over time.
>
> While at this, re-use the notifiers for UP/SMP since on
> UP machine or UP_ON_SMP policy->cpus mask would contain only
> the boot CPU.
>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
> [santosh.shilimkar@ti.com: re-based against omap cpufreq
> upstream branch and fixed notifiers]
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> Cc: Kevin Hilman <khilman@ti.com>

Thanks, applied to pm-wip/cpufreq branch.

Kevin

> ---
> Patch is outcome of below discussion.
> http://www.mail-archive.com/linux-omap@vger.kernel.org/msg51559.html
>
>  arch/arm/mach-omap2/omap2plus-cpufreq.c |   50 ++++++++++++++++--------------
>  1 files changed, 27 insertions(+), 23 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/omap2plus-cpufreq.c b/arch/arm/mach-omap2/omap2plus-cpufreq.c
> index 1f3b2e1..de82e87 100644
> --- a/arch/arm/mach-omap2/omap2plus-cpufreq.c
> +++ b/arch/arm/mach-omap2/omap2plus-cpufreq.c
> @@ -38,6 +38,16 @@
>  
>  #include <mach/hardware.h>
>  
> +#ifdef CONFIG_SMP
> +struct lpj_info {
> +	unsigned long	ref;
> +	unsigned int	freq;
> +};
> +
> +static DEFINE_PER_CPU(struct lpj_info, lpj_ref);
> +static struct lpj_info global_lpj_ref;
> +#endif
> +
>  static struct cpufreq_frequency_table *freq_table;
>  static atomic_t freq_table_users = ATOMIC_INIT(0);
>  static struct clk *mpu_clk;
> @@ -96,37 +106,18 @@ static int omap_target(struct cpufreq_policy *policy,
>  	if (freqs.old == freqs.new && policy->cur == freqs.new)
>  		return ret;
>  
> -	if (!is_smp()) {
> -		cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
> -		goto set_freq;
> -	}
> -
>  	/* notifiers */
>  	for_each_cpu(i, policy->cpus) {
>  		freqs.cpu = i;
>  		cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
>  	}
>  
> -set_freq:
>  #ifdef CONFIG_CPU_FREQ_DEBUG
>  	pr_info("cpufreq-omap: transition: %u --> %u\n", freqs.old, freqs.new);
>  #endif
>  
>  	ret = clk_set_rate(mpu_clk, freqs.new * 1000);
> -
> -	/*
> -	 * Generic CPUFREQ driver jiffy update is under !SMP. So jiffies
> -	 * won't get updated when UP machine cpufreq build with
> -	 * CONFIG_SMP enabled. Below code is added only to manage that
> -	 * scenario
> -	 */
>  	freqs.new = omap_getspeed(policy->cpu);
> -	if (!is_smp()) {
> -		loops_per_jiffy =
> -			 cpufreq_scale(loops_per_jiffy, freqs.old, freqs.new);
> -		cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
> -		goto skip_lpj;
> -	}
>  
>  #ifdef CONFIG_SMP
>  	/*
> @@ -134,10 +125,24 @@ set_freq:
>  	 * cpufreq driver. So, update the per-CPU loops_per_jiffy value
>  	 * on frequency transition. We need to update all dependent CPUs.
>  	 */
> -	for_each_cpu(i, policy->cpus)
> +	for_each_cpu(i, policy->cpus) {
> +		struct lpj_info *lpj = &per_cpu(lpj_ref, i);
> +		if (!lpj->freq) {
> +			lpj->ref = per_cpu(cpu_data, i).loops_per_jiffy;
> +			lpj->freq = freqs.old;
> +		}
> +
>  		per_cpu(cpu_data, i).loops_per_jiffy =
> -			cpufreq_scale(per_cpu(cpu_data, i).loops_per_jiffy,
> -					freqs.old, freqs.new);
> +			cpufreq_scale(lpj->ref, lpj->freq, freqs.new);
> +	}
> +
> +	/* And don't forget to adjust the global one */
> +	if (!global_lpj_ref.freq) {
> +		global_lpj_ref.ref = loops_per_jiffy;
> +		global_lpj_ref.freq = freqs.old;
> +	}
> +	loops_per_jiffy = cpufreq_scale(global_lpj_ref.ref, global_lpj_ref.freq,
> +					freqs.new);
>  #endif
>  
>  	/* notifiers */
> @@ -146,7 +151,6 @@ set_freq:
>  		cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
>  	}
>  
> -skip_lpj:
>  	return ret;
>  }