Re: [PATCH 5/8] acpi-cpufreq: Add support for disabling dynamic overclocking

[Rafael J. Wysocki]

On Thursday, July 26, 2012, Andre Przywara wrote:
> One feature present in powernow-k8 that isn't present in acpi-cpufreq
> is support for enabling or disabling AMD's core performance boost
> technology. This patch adds support to acpi-cpufreq, but also
> includes support for Intel's dynamic acceleration.
> 
> The original boost disabling sysfs file was per CPU, but acted
> globally. Also the naming (cpb) was at least not intuitive.
> So lets introduce a single file simply called "boost", which sits
> once in /sys/devices/system/cpu/cpufreq. This should be the
> documented and approved way of using this feature.
> 
> A following patch will re-introduce the cpb knob for compatibility
> reasons on AMD CPUs.
> 
> Per-CPU boost switching is possible, but not trivial and is thus
> postponed to a later patch series.
> 
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>

Len, Dave, any comments and/or objections here?

Rafael


> ---
>  drivers/cpufreq/acpi-cpufreq.c |  177 ++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 177 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index ea949b8..ca41aaa 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -61,6 +61,8 @@ enum {
>  #define INTEL_MSR_RANGE		(0xffff)
>  #define AMD_MSR_RANGE		(0x7)
>  
> +#define MSR_K7_HWCR_CPB_DIS	(1ULL << 25)
> +
>  struct acpi_cpufreq_data {
>  	struct acpi_processor_performance *acpi_data;
>  	struct cpufreq_frequency_table *freq_table;
> @@ -76,6 +78,96 @@ static struct acpi_processor_performance __percpu *acpi_perf_data;
>  static struct cpufreq_driver acpi_cpufreq_driver;
>  
>  static unsigned int acpi_pstate_strict;
> +static bool boost_enabled, boost_supported;
> +static struct msr __percpu *msrs;
> +
> +static bool boost_state(unsigned int cpu)
> +{
> +	u32 lo, hi;
> +	u64 msr;
> +
> +	switch (boot_cpu_data.x86_vendor) {
> +	case X86_VENDOR_INTEL:
> +		rdmsr_on_cpu(cpu, MSR_IA32_MISC_ENABLE, &lo, &hi);
> +		msr = lo | ((u64)hi << 32);
> +		return !(msr & MSR_IA32_MISC_ENABLE_TURBO_DISABLE);
> +	case X86_VENDOR_AMD:
> +		rdmsr_on_cpu(cpu, MSR_K7_HWCR, &lo, &hi);
> +		msr = lo | ((u64)hi << 32);
> +		return !(msr & MSR_K7_HWCR_CPB_DIS);
> +	}
> +	return false;
> +}
> +
> +static void boost_set_msrs(bool enable, const struct cpumask *cpumask)
> +{
> +	u32 cpu;
> +	u32 msr_addr;
> +	u64 msr_mask;
> +
> +	switch (boot_cpu_data.x86_vendor) {
> +	case X86_VENDOR_INTEL:
> +		msr_addr = MSR_IA32_MISC_ENABLE;
> +		msr_mask = MSR_IA32_MISC_ENABLE_TURBO_DISABLE;
> +		break;
> +	case X86_VENDOR_AMD:
> +		msr_addr = MSR_K7_HWCR;
> +		msr_mask = MSR_K7_HWCR_CPB_DIS;
> +		break;
> +	default:
> +		return;
> +	}
> +
> +	rdmsr_on_cpus(cpumask, msr_addr, msrs);
> +
> +	for_each_cpu(cpu, cpumask) {
> +		struct msr *reg = per_cpu_ptr(msrs, cpu);
> +		if (enable)
> +			reg->q &= ~msr_mask;
> +		else
> +			reg->q |= msr_mask;
> +	}
> +
> +	wrmsr_on_cpus(cpumask, msr_addr, msrs);
> +}
> +
> +static ssize_t store_global_boost(struct kobject *kobj, struct attribute *attr,
> +				  const char *buf, size_t count)
> +{
> +	int ret;
> +	unsigned long val = 0;
> +
> +	if (!boost_supported)
> +		return -EINVAL;
> +
> +	ret = kstrtoul(buf, 10, &val);
> +	if (ret || (val > 1))
> +		return -EINVAL;
> +
> +	if ((val && boost_enabled) || (!val && !boost_enabled))
> +		return count;
> +
> +	get_online_cpus();
> +
> +	boost_set_msrs(val, cpu_online_mask);
> +
> +	put_online_cpus();
> +
> +	boost_enabled = val;
> +	pr_debug("Core Boosting %sabled.\n", val ? "en" : "dis");
> +
> +	return count;
> +}
> +
> +static ssize_t show_global_boost(struct kobject *kobj,
> +				 struct attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%u\n", boost_enabled);
> +}
> +
> +static struct global_attr global_boost = __ATTR(boost, 0644,
> +						show_global_boost,
> +						store_global_boost);
>  
>  static int check_est_cpu(unsigned int cpuid)
>  {
> @@ -446,6 +538,44 @@ static void free_acpi_perf_data(void)
>  	free_percpu(acpi_perf_data);
>  }
>  
> +static int boost_notify(struct notifier_block *nb, unsigned long action,
> +		      void *hcpu)
> +{
> +	unsigned cpu = (long)hcpu;
> +	const struct cpumask *cpumask;
> +
> +	cpumask = get_cpu_mask(cpu);
> +
> +	/*
> +	 * Clear the boost-disable bit on the CPU_DOWN path so that
> +	 * this cpu cannot block the remaining ones from boosting. On
> +	 * the CPU_UP path we simply keep the boost-disable flag in
> +	 * sync with the current global state.
> +	 */
> +
> +	switch (action) {
> +	case CPU_UP_PREPARE:
> +	case CPU_UP_PREPARE_FROZEN:
> +		boost_set_msrs(boost_enabled, cpumask);
> +		break;
> +
> +	case CPU_DOWN_PREPARE:
> +	case CPU_DOWN_PREPARE_FROZEN:
> +		boost_set_msrs(1, cpumask);
> +		break;
> +
> +	default:
> +		break;
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +
> +static struct notifier_block boost_nb = {
> +	.notifier_call          = boost_notify,
> +};
> +
>  /*
>   * acpi_cpufreq_early_init - initialize ACPI P-States library
>   *
> @@ -772,6 +902,49 @@ static struct cpufreq_driver acpi_cpufreq_driver = {
>  	.attr		= acpi_cpufreq_attr,
>  };
>  
> +static void __init acpi_cpufreq_boost_init(void)
> +{
> +	if (boot_cpu_has(X86_FEATURE_CPB) || boot_cpu_has(X86_FEATURE_IDA)) {
> +		msrs = msrs_alloc();
> +
> +		if (!msrs)
> +			return;
> +
> +		boost_supported = true;
> +		boost_enabled = boost_state(0);
> +
> +		get_online_cpus();
> +
> +		/* Force all MSRs to the same value */
> +		boost_set_msrs(boost_enabled, cpu_online_mask);
> +
> +		register_cpu_notifier(&boost_nb);
> +
> +		put_online_cpus();
> +	} else
> +		global_boost.attr.mode = 0444;
> +
> +	/* We create the boost file in any case, though for systems without
> +	 * hardware support it will be read-only and hardwired to return 0.
> +	 */
> +	if (sysfs_create_file(cpufreq_global_kobject, &(global_boost.attr)))
> +		pr_warn("could not register global boost sysfs file\n");
> +	else
> +		pr_debug("registered global boost sysfs file\n");
> +}
> +
> +static void __exit acpi_cpufreq_boost_exit(void)
> +{
> +	sysfs_remove_file(cpufreq_global_kobject, &(global_boost.attr));
> +
> +	if (msrs) {
> +		unregister_cpu_notifier(&boost_nb);
> +
> +		msrs_free(msrs);
> +		msrs = NULL;
> +	}
> +}
> +
>  static int __init acpi_cpufreq_init(void)
>  {
>  	int ret;
> @@ -789,6 +962,8 @@ static int __init acpi_cpufreq_init(void)
>  	if (ret)
>  		free_acpi_perf_data();
>  
> +	acpi_cpufreq_boost_init();
> +
>  	return ret;
>  }
>  
> @@ -796,6 +971,8 @@ static void __exit acpi_cpufreq_exit(void)
>  {
>  	pr_debug("acpi_cpufreq_exit\n");
>  
> +	acpi_cpufreq_boost_exit();
> +
>  	cpufreq_unregister_driver(&acpi_cpufreq_driver);
>  
>  	free_acpi_perf_data();
> 

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