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Revert "cpufreq: CPPC: Add support for frequency invariance"
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This reverts commit 4c38f2d.

There are few races in the frequency invariance support for CPPC driver,
namely the driver doesn't stop the kthread_work and irq_work on policy
exit during suspend/resume or CPU hotplug.

A proper fix won't be possible for the 5.13-rc, as it requires a lot of
changes. Lets revert the patch instead for now.

Fixes: 4c38f2d ("cpufreq: CPPC: Add support for frequency invariance")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Viresh Kumar authored and Rafael J. Wysocki committed Jun 14, 2021
1 parent 009c9aa commit 771fac5
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Showing 4 changed files with 12 additions and 245 deletions.
10 changes: 0 additions & 10 deletions drivers/cpufreq/Kconfig.arm
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Original file line number Diff line number Diff line change
Expand Up @@ -19,16 +19,6 @@ config ACPI_CPPC_CPUFREQ

If in doubt, say N.

config ACPI_CPPC_CPUFREQ_FIE
bool "Frequency Invariance support for CPPC cpufreq driver"
depends on ACPI_CPPC_CPUFREQ && GENERIC_ARCH_TOPOLOGY
default y
help
This extends frequency invariance support in the CPPC cpufreq driver,
by using CPPC delivered and reference performance counters.

If in doubt, say N.

config ARM_ALLWINNER_SUN50I_CPUFREQ_NVMEM
tristate "Allwinner nvmem based SUN50I CPUFreq driver"
depends on ARCH_SUNXI
Expand Down
245 changes: 12 additions & 233 deletions drivers/cpufreq/cppc_cpufreq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -10,18 +10,14 @@

#define pr_fmt(fmt) "CPPC Cpufreq:" fmt

#include <linux/arch_topology.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/dmi.h>
#include <linux/irq_work.h>
#include <linux/kthread.h>
#include <linux/time.h>
#include <linux/vmalloc.h>
#include <uapi/linux/sched/types.h>

#include <asm/unaligned.h>

Expand Down Expand Up @@ -61,204 +57,6 @@ static struct cppc_workaround_oem_info wa_info[] = {
}
};

#ifdef CONFIG_ACPI_CPPC_CPUFREQ_FIE

/* Frequency invariance support */
struct cppc_freq_invariance {
int cpu;
struct irq_work irq_work;
struct kthread_work work;
struct cppc_perf_fb_ctrs prev_perf_fb_ctrs;
struct cppc_cpudata *cpu_data;
};

static DEFINE_PER_CPU(struct cppc_freq_invariance, cppc_freq_inv);
static struct kthread_worker *kworker_fie;
static bool fie_disabled;

static struct cpufreq_driver cppc_cpufreq_driver;
static unsigned int hisi_cppc_cpufreq_get_rate(unsigned int cpu);
static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data,
struct cppc_perf_fb_ctrs fb_ctrs_t0,
struct cppc_perf_fb_ctrs fb_ctrs_t1);

/**
* cppc_scale_freq_workfn - CPPC arch_freq_scale updater for frequency invariance
* @work: The work item.
*
* The CPPC driver register itself with the topology core to provide its own
* implementation (cppc_scale_freq_tick()) of topology_scale_freq_tick() which
* gets called by the scheduler on every tick.
*
* Note that the arch specific counters have higher priority than CPPC counters,
* if available, though the CPPC driver doesn't need to have any special
* handling for that.
*
* On an invocation of cppc_scale_freq_tick(), we schedule an irq work (since we
* reach here from hard-irq context), which then schedules a normal work item
* and cppc_scale_freq_workfn() updates the per_cpu arch_freq_scale variable
* based on the counter updates since the last tick.
*/
static void cppc_scale_freq_workfn(struct kthread_work *work)
{
struct cppc_freq_invariance *cppc_fi;
struct cppc_perf_fb_ctrs fb_ctrs = {0};
struct cppc_cpudata *cpu_data;
unsigned long local_freq_scale;
u64 perf;

cppc_fi = container_of(work, struct cppc_freq_invariance, work);
cpu_data = cppc_fi->cpu_data;

if (cppc_get_perf_ctrs(cppc_fi->cpu, &fb_ctrs)) {
pr_warn("%s: failed to read perf counters\n", __func__);
return;
}

cppc_fi->prev_perf_fb_ctrs = fb_ctrs;
perf = cppc_perf_from_fbctrs(cpu_data, cppc_fi->prev_perf_fb_ctrs,
fb_ctrs);

perf <<= SCHED_CAPACITY_SHIFT;
local_freq_scale = div64_u64(perf, cpu_data->perf_caps.highest_perf);
if (WARN_ON(local_freq_scale > 1024))
local_freq_scale = 1024;

per_cpu(arch_freq_scale, cppc_fi->cpu) = local_freq_scale;
}

static void cppc_irq_work(struct irq_work *irq_work)
{
struct cppc_freq_invariance *cppc_fi;

cppc_fi = container_of(irq_work, struct cppc_freq_invariance, irq_work);
kthread_queue_work(kworker_fie, &cppc_fi->work);
}

static void cppc_scale_freq_tick(void)
{
struct cppc_freq_invariance *cppc_fi = &per_cpu(cppc_freq_inv, smp_processor_id());

/*
* cppc_get_perf_ctrs() can potentially sleep, call that from the right
* context.
*/
irq_work_queue(&cppc_fi->irq_work);
}

static struct scale_freq_data cppc_sftd = {
.source = SCALE_FREQ_SOURCE_CPPC,
.set_freq_scale = cppc_scale_freq_tick,
};

static void cppc_freq_invariance_policy_init(struct cpufreq_policy *policy,
struct cppc_cpudata *cpu_data)
{
struct cppc_perf_fb_ctrs fb_ctrs = {0};
struct cppc_freq_invariance *cppc_fi;
int i, ret;

if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
return;

if (fie_disabled)
return;

for_each_cpu(i, policy->cpus) {
cppc_fi = &per_cpu(cppc_freq_inv, i);
cppc_fi->cpu = i;
cppc_fi->cpu_data = cpu_data;
kthread_init_work(&cppc_fi->work, cppc_scale_freq_workfn);
init_irq_work(&cppc_fi->irq_work, cppc_irq_work);

ret = cppc_get_perf_ctrs(i, &fb_ctrs);
if (ret) {
pr_warn("%s: failed to read perf counters: %d\n",
__func__, ret);
fie_disabled = true;
} else {
cppc_fi->prev_perf_fb_ctrs = fb_ctrs;
}
}
}

static void __init cppc_freq_invariance_init(void)
{
struct sched_attr attr = {
.size = sizeof(struct sched_attr),
.sched_policy = SCHED_DEADLINE,
.sched_nice = 0,
.sched_priority = 0,
/*
* Fake (unused) bandwidth; workaround to "fix"
* priority inheritance.
*/
.sched_runtime = 1000000,
.sched_deadline = 10000000,
.sched_period = 10000000,
};
int ret;

if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
return;

if (fie_disabled)
return;

kworker_fie = kthread_create_worker(0, "cppc_fie");
if (IS_ERR(kworker_fie))
return;

ret = sched_setattr_nocheck(kworker_fie->task, &attr);
if (ret) {
pr_warn("%s: failed to set SCHED_DEADLINE: %d\n", __func__,
ret);
kthread_destroy_worker(kworker_fie);
return;
}

/* Register for freq-invariance */
topology_set_scale_freq_source(&cppc_sftd, cpu_present_mask);
}

static void cppc_freq_invariance_exit(void)
{
struct cppc_freq_invariance *cppc_fi;
int i;

if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
return;

if (fie_disabled)
return;

topology_clear_scale_freq_source(SCALE_FREQ_SOURCE_CPPC, cpu_present_mask);

for_each_possible_cpu(i) {
cppc_fi = &per_cpu(cppc_freq_inv, i);
irq_work_sync(&cppc_fi->irq_work);
}

kthread_destroy_worker(kworker_fie);
kworker_fie = NULL;
}

#else
static inline void
cppc_freq_invariance_policy_init(struct cpufreq_policy *policy,
struct cppc_cpudata *cpu_data)
{
}

static inline void cppc_freq_invariance_init(void)
{
}

static inline void cppc_freq_invariance_exit(void)
{
}
#endif /* CONFIG_ACPI_CPPC_CPUFREQ_FIE */

/* Callback function used to retrieve the max frequency from DMI */
static void cppc_find_dmi_mhz(const struct dmi_header *dm, void *private)
{
Expand Down Expand Up @@ -547,12 +345,9 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
cpu_data->perf_ctrls.desired_perf = caps->highest_perf;

ret = cppc_set_perf(cpu, &cpu_data->perf_ctrls);
if (ret) {
if (ret)
pr_debug("Err setting perf value:%d on CPU:%d. ret:%d\n",
caps->highest_perf, cpu, ret);
} else {
cppc_freq_invariance_policy_init(policy, cpu_data);
}

return ret;
}
Expand All @@ -565,12 +360,12 @@ static inline u64 get_delta(u64 t1, u64 t0)
return (u32)t1 - (u32)t0;
}

static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data,
struct cppc_perf_fb_ctrs fb_ctrs_t0,
struct cppc_perf_fb_ctrs fb_ctrs_t1)
static int cppc_get_rate_from_fbctrs(struct cppc_cpudata *cpu_data,
struct cppc_perf_fb_ctrs fb_ctrs_t0,
struct cppc_perf_fb_ctrs fb_ctrs_t1)
{
u64 delta_reference, delta_delivered;
u64 reference_perf;
u64 reference_perf, delivered_perf;

reference_perf = fb_ctrs_t0.reference_perf;

Expand All @@ -579,21 +374,12 @@ static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data,
delta_delivered = get_delta(fb_ctrs_t1.delivered,
fb_ctrs_t0.delivered);

/* Check to avoid divide-by zero and invalid delivered_perf */
if (!delta_reference || !delta_delivered)
return cpu_data->perf_ctrls.desired_perf;

return (reference_perf * delta_delivered) / delta_reference;
}

static int cppc_get_rate_from_fbctrs(struct cppc_cpudata *cpu_data,
struct cppc_perf_fb_ctrs fb_ctrs_t0,
struct cppc_perf_fb_ctrs fb_ctrs_t1)
{
u64 delivered_perf;

delivered_perf = cppc_perf_from_fbctrs(cpu_data, fb_ctrs_t0,
fb_ctrs_t1);
/* Check to avoid divide-by zero */
if (delta_reference || delta_delivered)
delivered_perf = (reference_perf * delta_delivered) /
delta_reference;
else
delivered_perf = cpu_data->perf_ctrls.desired_perf;

return cppc_cpufreq_perf_to_khz(cpu_data, delivered_perf);
}
Expand Down Expand Up @@ -718,20 +504,14 @@ static void cppc_check_hisi_workaround(void)

static int __init cppc_cpufreq_init(void)
{
int ret;

if ((acpi_disabled) || !acpi_cpc_valid())
return -ENODEV;

INIT_LIST_HEAD(&cpu_data_list);

cppc_check_hisi_workaround();

ret = cpufreq_register_driver(&cppc_cpufreq_driver);
if (!ret)
cppc_freq_invariance_init();

return ret;
return cpufreq_register_driver(&cppc_cpufreq_driver);
}

static inline void free_cpu_data(void)
Expand All @@ -748,7 +528,6 @@ static inline void free_cpu_data(void)

static void __exit cppc_cpufreq_exit(void)
{
cppc_freq_invariance_exit();
cpufreq_unregister_driver(&cppc_cpufreq_driver);

free_cpu_data();
Expand Down
1 change: 0 additions & 1 deletion include/linux/arch_topology.h
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,6 @@ bool topology_scale_freq_invariant(void);
enum scale_freq_source {
SCALE_FREQ_SOURCE_CPUFREQ = 0,
SCALE_FREQ_SOURCE_ARCH,
SCALE_FREQ_SOURCE_CPPC,
};

struct scale_freq_data {
Expand Down
1 change: 0 additions & 1 deletion kernel/sched/core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6389,7 +6389,6 @@ int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
{
return __sched_setscheduler(p, attr, false, true);
}
EXPORT_SYMBOL_GPL(sched_setattr_nocheck);

/**
* sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
Expand Down

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