[PATCH v5] cpufreq: Add SFI based cpufreq driver support

[PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Srinidhi Kasagar]

This adds the SFI based cpu freq driver for some of the Intel's
Silvermont based Atom architectures like Z34xx and Z35xx.

Signed-off-by: Rudramuni, Vishwesh M <vishwesh.m.rudramuni@intel.com>
Signed-off-by: Srinidhi Kasagar <srinidhi.kasagar@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---
v2:
(v2-v3: comments from Viresh)
* rephrase the Kconfig text
* merge the header file as its not being shared with anyone
* remove the unnecessary checks in sfi_cpufreq_target
* style changes in kzalloc
* fix the potential memory leak sfi_cpufreq_cpu_init
* move the cpufreq driver flag to the structure definition
* remove the redundant init of policy->cpu and policy->cur
* remove the unnecessary check while init the freq table
* merge the for loops in cpu_init
* use cpufreq_generic_attr rather than the custom one

v3:
* Add this change log
* remove the left over not used cached_freq var
* merge yet another for loop in cpu_init

v4:
* remove unnecessary pr_debug
* rephrase Kconfig text
* remove unused macro SFI_CPU_MAX
* Add Viresh's Acked-by

v5:
(comments from Len Brown)
* rename few private functions with sfi_cpufreq_ prefix
* move the PERF_CTL_MASK to msr-index.h
* make the driver.get current freq to refer PERF_CTRL
* remove sfi_processor_px, rather reuse sfi_freq_table_entry
* remove unnecessary memcpy, rather just point to the freq table
* consolidate get_performance_states with parse_freq
* remove extract_freq and make get_cur_freq to read from MSR directly
* move the state_count check while registering the perf states

 arch/x86/include/uapi/asm/msr-index.h |    1 +
 drivers/cpufreq/Kconfig.x86           |   10 ++
 drivers/cpufreq/Makefile              |    1 +
 drivers/cpufreq/sfi-cpufreq.c         |  238 +++++++++++++++++++++++++++++++++
 4 files changed, 250 insertions(+)
 create mode 100644 drivers/cpufreq/sfi-cpufreq.c

diff --git a/arch/x86/include/uapi/asm/msr-index.h b/arch/x86/include/uapi/asm/msr-index.h
index e21331ce368f..4f6dae67dd10 100644
--- a/arch/x86/include/uapi/asm/msr-index.h
+++ b/arch/x86/include/uapi/asm/msr-index.h
@@ -318,6 +318,7 @@
 
 #define MSR_IA32_PERF_STATUS		0x00000198
 #define MSR_IA32_PERF_CTL		0x00000199
+#define INTEL_PERF_CTL_MASK		0xffff
 #define MSR_AMD_PSTATE_DEF_BASE		0xc0010064
 #define MSR_AMD_PERF_STATUS		0xc0010063
 #define MSR_AMD_PERF_CTL		0xc0010062
diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
index 89ae88f91895..dd2b6f541f33 100644
--- a/drivers/cpufreq/Kconfig.x86
+++ b/drivers/cpufreq/Kconfig.x86
@@ -57,6 +57,16 @@ config X86_ACPI_CPUFREQ_CPB
 	  By enabling this option the acpi_cpufreq driver provides the old
 	  entry in addition to the new boost ones, for compatibility reasons.
 
+config X86_SFI_CPUFREQ
+	tristate "SFI P-States driver"
+	depends on X86_INTEL_MID && SFI
+	help
+	  This adds a CPUFreq driver for some Silvermont based Intel Atom
+	  architectures like Z34xx and Z35xx which enumerate processor
+	  performance states through SFI.
+
+	  If in doubt, say N.
+
 config ELAN_CPUFREQ
 	tristate "AMD Elan SC400 and SC410"
 	depends on MELAN
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index db6d9a2fea4d..c3b51efd4a85 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_X86_P4_CLOCKMOD)		+= p4-clockmod.o
 obj-$(CONFIG_X86_CPUFREQ_NFORCE2)	+= cpufreq-nforce2.o
 obj-$(CONFIG_X86_INTEL_PSTATE)		+= intel_pstate.o
 obj-$(CONFIG_X86_AMD_FREQ_SENSITIVITY)	+= amd_freq_sensitivity.o
+obj-$(CONFIG_X86_SFI_CPUFREQ)		+= sfi-cpufreq.o
 
 ##################################################################################
 # ARM SoC drivers
diff --git a/drivers/cpufreq/sfi-cpufreq.c b/drivers/cpufreq/sfi-cpufreq.c
new file mode 100644
index 000000000000..83f865f7b1e0
--- /dev/null
+++ b/drivers/cpufreq/sfi-cpufreq.c
@@ -0,0 +1,238 @@
+/*
+ *  SFI Processor P-States Driver
+ *  Based on ACPI Processor P-States Driver
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  Author: Vishwesh M Rudramuni <vishwesh.m.rudramuni@intel.com>
+ *  Author: Srinidhi Kasagar <srinidhi.kasagar@intel.com>
+ */
+
+#include <linux/cpufreq.h>
+#include <linux/cpuidle.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sfi.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+
+#include <asm/msr.h>
+#include <asm/processor.h>
+
+#define SFI_FREQ_MASK		0xff00
+
+static DEFINE_PER_CPU(struct sfi_cpufreq_data *, drv_data);
+static DEFINE_MUTEX(performance_mutex);
+
+static struct sfi_freq_table_entry *f_entry;
+/* sfi_perf_data is a pointer to percpu data. */
+static struct sfi_cpufreq_performance *sfi_perf_data;
+
+static int sfi_cpufreq_num;
+
+struct sfi_cpufreq_performance {
+	unsigned int state;
+	unsigned int state_count;
+	struct sfi_freq_table_entry *states;
+};
+
+struct sfi_cpufreq_data {
+	struct sfi_cpufreq_performance *sfi_data;
+	struct cpufreq_frequency_table *freq_table;
+};
+
+static int parse_freq(struct sfi_table_header *table)
+{
+	struct sfi_table_simple *sb;
+
+	sb = (struct sfi_table_simple *)table;
+
+	sfi_cpufreq_num = SFI_GET_NUM_ENTRIES(sb, struct sfi_freq_table_entry);
+	f_entry = (struct sfi_freq_table_entry *)sb->pentry;
+
+	return 0;
+}
+
+static int sfi_cpufreq_register_performance(struct sfi_cpufreq_performance *pr)
+{
+	mutex_lock(&performance_mutex);
+
+	/* parse the freq table from SFI */
+	sfi_table_parse(SFI_SIG_FREQ, NULL, NULL, parse_freq);
+
+	pr->state_count = sfi_cpufreq_num;
+	if (pr->state_count <= 1) {
+		pr_err("No p-states discovered\n");
+		return -ENODEV;
+	}
+
+	pr->states = f_entry;
+
+	mutex_unlock(&performance_mutex);
+
+	return 0;
+}
+
+static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
+{
+	u32 lo, hi, sfi_ctrl;
+	struct sfi_cpufreq_performance *perf;
+	struct cpufreq_frequency_table *pos;
+	struct sfi_cpufreq_data *data = per_cpu(drv_data, cpu);
+
+	rdmsr_on_cpu(cpu, MSR_IA32_PERF_CTL, &lo, &hi);
+	lo &= SFI_FREQ_MASK;
+
+	perf = data->sfi_data;
+
+	cpufreq_for_each_entry(pos, data->freq_table) {
+		sfi_ctrl = perf->states[pos->driver_data].ctrl_val
+			& SFI_FREQ_MASK;
+		if (sfi_ctrl == lo)
+			return pos->frequency;
+	}
+	return data->freq_table[0].frequency;
+}
+
+static int sfi_cpufreq_target(struct cpufreq_policy *policy,
+				unsigned int index)
+{
+	struct sfi_cpufreq_data *data = per_cpu(drv_data, policy->cpu);
+	struct sfi_cpufreq_performance *perf;
+	unsigned int next_perf_state = 0; /* Index into perf table */
+	u32 lo, hi;
+
+	perf = data->sfi_data;
+	next_perf_state = data->freq_table[index].driver_data;
+
+	rdmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, &lo, &hi);
+	lo = (lo & ~INTEL_PERF_CTL_MASK) |
+		((u32) perf->states[next_perf_state].ctrl_val &
+			INTEL_PERF_CTL_MASK);
+	wrmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, lo, hi);
+
+	perf->state = next_perf_state;
+
+	return 0;
+}
+
+static int sfi_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+	unsigned int i, result = 0, valid_states = 0;
+	unsigned int cpu = policy->cpu;
+	struct sfi_cpufreq_data *data;
+	struct sfi_cpufreq_performance *perf;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->sfi_data = per_cpu_ptr(sfi_perf_data, cpu);
+	per_cpu(drv_data, cpu) = data;
+
+	result = sfi_cpufreq_register_performance(data->sfi_data);
+	if (result)
+		goto err_free;
+
+	perf = data->sfi_data;
+	policy->shared_type = CPUFREQ_SHARED_TYPE_HW;
+
+	data->freq_table = kzalloc(sizeof(*data->freq_table) *
+				(perf->state_count+1), GFP_KERNEL);
+	if (!data->freq_table) {
+		result = -ENOMEM;
+		goto err_free;
+	}
+
+	policy->cpuinfo.transition_latency = 0;
+	for (i = 0; i < perf->state_count; i++) {
+		/* detect transition latency */
+		if ((perf->states[i].latency * 1000) >
+		    policy->cpuinfo.transition_latency)
+			policy->cpuinfo.transition_latency =
+				perf->states[i].latency * 1000;
+
+		/* initialize the freq table */
+		data->freq_table[valid_states].driver_data = i;
+		data->freq_table[valid_states].frequency =
+				perf->states[i].freq_mhz * 1000;
+		valid_states++;
+
+		pr_debug("     %cP%d: %d MHz, %d uS\n",
+			(i == perf->state ? '*' : ' '), i,
+			(u32) perf->states[i].freq_mhz,
+			(u32) perf->states[i].latency);
+	}
+
+	data->freq_table[valid_states].frequency = CPUFREQ_TABLE_END;
+	perf->state = 0;
+
+	result = cpufreq_table_validate_and_show(policy, data->freq_table);
+	if (result)
+		goto err_freqfree;
+
+	pr_debug("CPU%u - SFI performance management activated.\n", cpu);
+
+	return result;
+
+err_freqfree:
+	kfree(data->freq_table);
+err_free:
+	kfree(data);
+	per_cpu(drv_data, cpu) = NULL;
+
+	return result;
+}
+
+static int sfi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
+{
+	struct sfi_cpufreq_data *data = per_cpu(drv_data, policy->cpu);
+
+	per_cpu(drv_data, policy->cpu) = NULL;
+	kfree(data->freq_table);
+	kfree(data);
+
+	return 0;
+}
+
+static struct cpufreq_driver sfi_cpufreq_driver = {
+	.flags		= CPUFREQ_CONST_LOOPS,
+	.get		= get_cur_freq_on_cpu,
+	.verify		= cpufreq_generic_frequency_table_verify,
+	.target_index	= sfi_cpufreq_target,
+	.init		= sfi_cpufreq_cpu_init,
+	.exit		= sfi_cpufreq_cpu_exit,
+	.name		= "sfi-cpufreq",
+	.attr		= cpufreq_generic_attr,
+};
+
+static int __init sfi_cpufreq_init(void)
+{
+	sfi_perf_data = alloc_percpu(struct sfi_cpufreq_performance);
+	if (!sfi_perf_data) {
+		pr_err("Memory allocation error for sfi_perf_data.\n");
+		return -ENOMEM;
+	}
+
+	return cpufreq_register_driver(&sfi_cpufreq_driver);
+}
+late_initcall(sfi_cpufreq_init);
+
+static void __exit sfi_cpufreq_exit(void)
+{
+	cpufreq_unregister_driver(&sfi_cpufreq_driver);
+	free_percpu(sfi_perf_data);
+}
+module_exit(sfi_cpufreq_exit);
+
+MODULE_AUTHOR("Vishwesh M Rudramuni <vishwesh.m.rudramuni@intel.com>");
+MODULE_DESCRIPTION("SFI P-States Driver");
+MODULE_LICENSE("GPL");
-- 
1.7.9.5


-- 

Re: [PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Kasagar, Srinidhi]

On Tue, Nov 18, 2014 at 11:15:45AM +0530, Srinidhi Kasagar wrote:
> This adds the SFI based cpu freq driver for some of the Intel's
> Silvermont based Atom architectures like Z34xx and Z35xx.
> 
> Signed-off-by: Rudramuni, Vishwesh M <vishwesh.m.rudramuni@intel.com>
> Signed-off-by: Srinidhi Kasagar <srinidhi.kasagar@intel.com>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> ---

[..]

> +static int sfi_cpufreq_register_performance(struct sfi_cpufreq_performance *pr)
> +{
> +	mutex_lock(&performance_mutex);
> +
> +	/* parse the freq table from SFI */
> +	sfi_table_parse(SFI_SIG_FREQ, NULL, NULL, parse_freq);
> +
> +	pr->state_count = sfi_cpufreq_num;
> +	if (pr->state_count <= 1) {
> +		pr_err("No p-states discovered\n");
> +		return -ENODEV;
Was in a hurry, will release the mutex in the next version. Let me
knmow if you have further comments.

Srinidhi

Re: [PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Viresh Kumar]

On 18 November 2014 11:15, Srinidhi Kasagar <srinidhi.kasagar@intel.com> wrote:
> diff --git a/drivers/cpufreq/sfi-cpufreq.c b/drivers/cpufreq/sfi-cpufreq.c
> +static int parse_freq(struct sfi_table_header *table)

When this can't fail, why should it return a int?

> +{
> +       struct sfi_table_simple *sb;
> +
> +       sb = (struct sfi_table_simple *)table;
> +
> +       sfi_cpufreq_num = SFI_GET_NUM_ENTRIES(sb, struct sfi_freq_table_entry);
> +       f_entry = (struct sfi_freq_table_entry *)sb->pentry;
> +
> +       return 0;
> +}
> +
> +static int sfi_cpufreq_register_performance(struct sfi_cpufreq_performance *pr)
> +{
> +       mutex_lock(&performance_mutex);
> +
> +       /* parse the freq table from SFI */
> +       sfi_table_parse(SFI_SIG_FREQ, NULL, NULL, parse_freq);
> +
> +       pr->state_count = sfi_cpufreq_num;
> +       if (pr->state_count <= 1) {
> +               pr_err("No p-states discovered\n");
> +               return -ENODEV;
> +       }
> +
> +       pr->states = f_entry;
> +
> +       mutex_unlock(&performance_mutex);
> +
> +       return 0;
> +}
> +
> +static unsigned int get_cur_freq_on_cpu(unsigned int cpu)
> +{
> +       u32 lo, hi, sfi_ctrl;
> +       struct sfi_cpufreq_performance *perf;
> +       struct cpufreq_frequency_table *pos;
> +       struct sfi_cpufreq_data *data = per_cpu(drv_data, cpu);
> +
> +       rdmsr_on_cpu(cpu, MSR_IA32_PERF_CTL, &lo, &hi);
> +       lo &= SFI_FREQ_MASK;
> +
> +       perf = data->sfi_data;
> +
> +       cpufreq_for_each_entry(pos, data->freq_table) {
> +               sfi_ctrl = perf->states[pos->driver_data].ctrl_val
> +                       & SFI_FREQ_MASK;
> +               if (sfi_ctrl == lo)
> +                       return pos->frequency;
> +       }
> +       return data->freq_table[0].frequency;
> +}
> +
> +static int sfi_cpufreq_target(struct cpufreq_policy *policy,
> +                               unsigned int index)
> +{
> +       struct sfi_cpufreq_data *data = per_cpu(drv_data, policy->cpu);
> +       struct sfi_cpufreq_performance *perf;
> +       unsigned int next_perf_state = 0; /* Index into perf table */
> +       u32 lo, hi;
> +
> +       perf = data->sfi_data;
> +       next_perf_state = data->freq_table[index].driver_data;
> +
> +       rdmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, &lo, &hi);
> +       lo = (lo & ~INTEL_PERF_CTL_MASK) |
> +               ((u32) perf->states[next_perf_state].ctrl_val &
> +                       INTEL_PERF_CTL_MASK);
> +       wrmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, lo, hi);
> +
> +       perf->state = next_perf_state;

Can use data->sfi_data->state = next_perf_state here directly and
drop local var 'perf'.

> +
> +       return 0;
> +}
> +
> +static int sfi_cpufreq_cpu_init(struct cpufreq_policy *policy)
> +{
> +       unsigned int i, result = 0, valid_states = 0;
> +       unsigned int cpu = policy->cpu;
> +       struct sfi_cpufreq_data *data;
> +       struct sfi_cpufreq_performance *perf;
> +
> +       data = kzalloc(sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return -ENOMEM;
> +
> +       data->sfi_data = per_cpu_ptr(sfi_perf_data, cpu);

I told you this before and this is still broken:

> Your code is dependent on policy->cpu at multiple places and it can change on
> CPU hotplug.

To explain again, in your case a single policy will have two CPUs.
Groups are: 0-1 and 2-3.
policy->cpu for both policies are 0 and 2.

If we hotplug out cpu 0 or cpu 2, policy->cpu will be updated to 1 and 3.

And then the above per-cpu variable access will return NULL, as you
have initialized
them just for 0 and 2, not 1 and 3.

> +       per_cpu(drv_data, cpu) = data;
> +
> +       result = sfi_cpufreq_register_performance(data->sfi_data);
> +       if (result)
> +               goto err_free;
> +
> +       perf = data->sfi_data;
> +       policy->shared_type = CPUFREQ_SHARED_TYPE_HW;
> +
> +       data->freq_table = kzalloc(sizeof(*data->freq_table) *
> +                               (perf->state_count+1), GFP_KERNEL);
> +       if (!data->freq_table) {
> +               result = -ENOMEM;
> +               goto err_free;
> +       }
> +
> +       policy->cpuinfo.transition_latency = 0;
> +       for (i = 0; i < perf->state_count; i++) {
> +               /* detect transition latency */
> +               if ((perf->states[i].latency * 1000) >
> +                   policy->cpuinfo.transition_latency)
> +                       policy->cpuinfo.transition_latency =
> +                               perf->states[i].latency * 1000;
> +
> +               /* initialize the freq table */
> +               data->freq_table[valid_states].driver_data = i;
> +               data->freq_table[valid_states].frequency =
> +                               perf->states[i].freq_mhz * 1000;
> +               valid_states++;
> +
> +               pr_debug("     %cP%d: %d MHz, %d uS\n",
> +                       (i == perf->state ? '*' : ' '), i,
> +                       (u32) perf->states[i].freq_mhz,
> +                       (u32) perf->states[i].latency);
> +       }
> +
> +       data->freq_table[valid_states].frequency = CPUFREQ_TABLE_END;
> +       perf->state = 0;
> +
> +       result = cpufreq_table_validate_and_show(policy, data->freq_table);
> +       if (result)
> +               goto err_freqfree;
> +
> +       pr_debug("CPU%u - SFI performance management activated.\n", cpu);
> +
> +       return result;
> +
> +err_freqfree:
> +       kfree(data->freq_table);
> +err_free:
> +       kfree(data);
> +       per_cpu(drv_data, cpu) = NULL;

Order of these two instructions must be reversed..

> +
> +       return result;
> +}
> +
> +static int sfi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
> +{
> +       struct sfi_cpufreq_data *data = per_cpu(drv_data, policy->cpu);
> +
> +       per_cpu(drv_data, policy->cpu) = NULL;
> +       kfree(data->freq_table);
> +       kfree(data);
> +
> +       return 0;
> +}
> +
> +static struct cpufreq_driver sfi_cpufreq_driver = {
> +       .flags          = CPUFREQ_CONST_LOOPS,
> +       .get            = get_cur_freq_on_cpu,
> +       .verify         = cpufreq_generic_frequency_table_verify,
> +       .target_index   = sfi_cpufreq_target,
> +       .init           = sfi_cpufreq_cpu_init,
> +       .exit           = sfi_cpufreq_cpu_exit,
> +       .name           = "sfi-cpufreq",
> +       .attr           = cpufreq_generic_attr,
> +};
> +
> +static int __init sfi_cpufreq_init(void)
> +{
> +       sfi_perf_data = alloc_percpu(struct sfi_cpufreq_performance);

Why do you need a per-cpu struct for this? Its per-policy and so you
better allocate it at runtime from ->init() call.

> +       if (!sfi_perf_data) {
> +               pr_err("Memory allocation error for sfi_perf_data.\n");
> +               return -ENOMEM;
> +       }
> +
> +       return cpufreq_register_driver(&sfi_cpufreq_driver);
> +}
> +late_initcall(sfi_cpufreq_init);
> +
> +static void __exit sfi_cpufreq_exit(void)
> +{
> +       cpufreq_unregister_driver(&sfi_cpufreq_driver);
> +       free_percpu(sfi_perf_data);
> +}
> +module_exit(sfi_cpufreq_exit);
> +
> +MODULE_AUTHOR("Vishwesh M Rudramuni <vishwesh.m.rudramuni@intel.com>");
> +MODULE_DESCRIPTION("SFI P-States Driver");
> +MODULE_LICENSE("GPL");
> --
> 1.7.9.5
>
>
> --

Re: [PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Kasagar, Srinidhi]

On Tue, Nov 18, 2014 at 04:33:47PM +0530, Viresh Kumar wrote:
> On 18 November 2014 11:15, Srinidhi Kasagar <srinidhi.kasagar@intel.com> wrote:
> > diff --git a/drivers/cpufreq/sfi-cpufreq.c b/drivers/cpufreq/sfi-cpufreq.c
> > +static int parse_freq(struct sfi_table_header *table)
> 

[..]

> > +
> > +static int sfi_cpufreq_cpu_init(struct cpufreq_policy *policy)
> > +{
> > +       unsigned int i, result = 0, valid_states = 0;
> > +       unsigned int cpu = policy->cpu;
> > +       struct sfi_cpufreq_data *data;
> > +       struct sfi_cpufreq_performance *perf;
> > +
> > +       data = kzalloc(sizeof(*data), GFP_KERNEL);
> > +       if (!data)
> > +               return -ENOMEM;
> > +
> > +       data->sfi_data = per_cpu_ptr(sfi_perf_data, cpu);
> 
> I told you this before and this is still broken:
> 
> > Your code is dependent on policy->cpu at multiple places and it can change on
> > CPU hotplug.
> 
> To explain again, in your case a single policy will have two CPUs.
> Groups are: 0-1 and 2-3.
> policy->cpu for both policies are 0 and 2.
Not anymore now..I have fixed it in my earlier version.

$ cat /sys/devices/system/cpu/cpu*/cpufreq/affected_cpus 
0
1
2
3

$  cat /sys/devices/system/cpu/cpu*/cpufreq/related_cpus   
0
1
2
3

> 
> If we hotplug out cpu 0 or cpu 2, policy->cpu will be updated to 1 and 3.
> 
> And then the above per-cpu variable access will return NULL, as you
> have initialized
> them just for 0 and 2, not 1 and 3.

Srinidhi

Re: [PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Viresh Kumar]

On 18 November 2014 22:51, Kasagar, Srinidhi <srinidhi.kasagar@intel.com> wrote:
> Not anymore now..I have fixed it in my earlier version.
>
> $ cat /sys/devices/system/cpu/cpu*/cpufreq/affected_cpus
> 0
> 1
> 2
> 3
>
> $  cat /sys/devices/system/cpu/cpu*/cpufreq/related_cpus
> 0
> 1
> 2
> 3

What do you mean by you have fixed it? Weren't the CPUs sharing clock lines?
I hope cpu 0 and 1 should be sharing their clock lines, i.e. they
change freq together.
Also same for cpu 2 and 3.

Re: [PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Kasagar, Srinidhi]

On Wed, Nov 19, 2014 at 01:03:38PM +0530, Viresh Kumar wrote:
> On 18 November 2014 22:51, Kasagar, Srinidhi <srinidhi.kasagar@intel.com> wrote:
> > Not anymore now..I have fixed it in my earlier version.
> >
> > $ cat /sys/devices/system/cpu/cpu*/cpufreq/affected_cpus
> > 0
> > 1
> > 2
> > 3
> >
> > $  cat /sys/devices/system/cpu/cpu*/cpufreq/related_cpus
> > 0
> > 1
> > 2
> > 3
> 
> What do you mean by you have fixed it? Weren't the CPUs sharing clock lines?
> I hope cpu 0 and 1 should be sharing their clock lines, i.e. they
> change freq together.
> Also same for cpu 2 and 3.
The architecture supports both, and the current code allows me
to change the freq independently and that's why the above
output lines.

Srinidhi

Re: [PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Viresh Kumar]

On 19 November 2014 15:15, Kasagar, Srinidhi <srinidhi.kasagar@intel.com> wrote:
> The architecture supports both, and the current code allows me
> to change the freq independently and that's why the above
> output lines.

Which part of the code exactly controls this ?

Re: [PATCH v5] cpufreq: Add SFI based cpufreq driver support

[Kasagar, Srinidhi]

On Wed, Nov 19, 2014 at 03:17:54PM +0530, Viresh Kumar wrote:
> On 19 November 2014 15:15, Kasagar, Srinidhi <srinidhi.kasagar@intel.com> wrote:
> > The architecture supports both, and the current code allows me
> > to change the freq independently and that's why the above
> > output lines.
> 
> Which part of the code exactly controls this ?
That's the default behavior and I need not have to control it.
What I did wrong was to report the output of out-of-my-tree kernel
which leads to this confusion..

Srinidhi