Hi,
On Thu, 2011-06-02 at 20:23 +0530, ext Santosh Shilimkar wrote:
> Missed Kevin in cc. :(
> Sorry about that.
>
> -------- Original Message --------
> Subject: [PATCH] OMAP2+: CPUfreq: Allow the CPU scaling when secondary
> CPUs are offline.
> Date: Thu, 2 Jun 2011 20:21:10 +0530
> From: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
> To: <linux-omap@xxxxxxxxxxxxxxx>
> CC: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
>
> Current OMAP2PLUS CPUfreq tagret() functions returns when all
> the CPU's are not online. This will break DVFS when secondary
> CPUs are offlined.
>
> The intention of that check was just avoid CPU frequency change
> during the window when CPU becomes online but it's cpufreq_init is
> not done yet.
>
> Fix the check accordingly.
>
> Thanks for Nishant Menon <nm@xxxxxx> for reporting it.
>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
> Reported-by: Nishanth Menon <nm@xxxxxx>
> Tested-by: Vishwanath BS <vishwanath.bs@xxxxxx>
> ---
> There were some question of making the variable atomic etc
> in an internal discussion. After some thinking, I realised
> there is no need of that since this is just a counter which
> maintains the count for online_cpus = cpufreq_init_cpus.
>
> arch/arm/mach-omap2/omap2plus-cpufreq.c | 9 ++++++++-
> 1 files changed, 8 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/omap2plus-cpufreq.c
> b/arch/arm/mach-omap2/omap2plus-cpufreq.c
> index 33a91ec..909bfcb 100644
> --- a/arch/arm/mach-omap2/omap2plus-cpufreq.c
> +++ b/arch/arm/mach-omap2/omap2plus-cpufreq.c
> @@ -44,6 +44,7 @@ static struct cpufreq_frequency_table *freq_table;
> static struct clk *mpu_clk;
> static char *mpu_clk_name;
> static struct device *mpu_dev;
> +static int cpus_initialized;
>
> static int omap_verify_speed(struct cpufreq_policy *policy)
> {
> @@ -82,7 +83,7 @@ static int omap_target(struct cpufreq_policy *policy,
> struct cpufreq_freqs freqs;
>
> /* Changes not allowed until all CPUs are online */
This comment are no more relevant and should be changed also...
> - if (is_smp() && (num_online_cpus() < NR_CPUS))
> + if (is_smp() && (cpus_initialized < num_online_cpus()))
> return ret;
>
> /* Ensure desired rate is within allowed range. Some govenors
> @@ -194,6 +195,8 @@ static int __cpuinit omap_cpu_init(struct
> cpufreq_policy *policy)
> policy->shared_type = CPUFREQ_SHARED_TYPE_ANY;
> cpumask_or(cpumask, cpumask_of(policy->cpu), cpumask);
> cpumask_copy(policy->cpus, cpumask);
> + cpus_initialized++;
> + smp_wmb();
> }
>
> /* FIXME: what's the actual transition time? */
> @@ -206,6 +209,10 @@ static int omap_cpu_exit(struct cpufreq_policy *policy)
> {
> clk_exit_cpufreq_table(&freq_table);
> clk_put(mpu_clk);
> + if (is_smp()) {
> + cpus_initialized--;
> + smp_wmb();
> + }
> return 0;
> }
>
Best Regards,
Igor Dmitriev
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