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Revert "cpufreq: intel_pstate: Use ACPI perf configuration"
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Revert commit 37afb00 (cpufreq: intel_pstate: Use ACPI perf
configuration) that is reported to cause a regression to happen
on a system where invalid data are returned by the ACPI _PSS object.

Since that commit makes assumptions regarding the _PSS output
correctness that may turn out to be overly optimistic in general,
there is a concern that it may introduce regression on more
systems, so it's better to revert it now and we'll revisit the
underlying issue in the next cycle with a more robust solution.

Conflicts:
        drivers/cpufreq/intel_pstate.c

Fixes: 37afb00 (cpufreq: intel_pstate: Use ACPI perf configuration)
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Rafael J. Wysocki committed Nov 18, 2015
1 parent 799281a commit 6ee11e4
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Showing 2 changed files with 1 addition and 171 deletions.
1 change: 0 additions & 1 deletion drivers/cpufreq/Kconfig.x86
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@
config X86_INTEL_PSTATE
bool "Intel P state control"
depends on X86
select ACPI_PROCESSOR if ACPI
help
This driver provides a P state for Intel core processors.
The driver implements an internal governor and will become
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171 changes: 1 addition & 170 deletions drivers/cpufreq/intel_pstate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -34,10 +34,6 @@
#include <asm/cpu_device_id.h>
#include <asm/cpufeature.h>

#if IS_ENABLED(CONFIG_ACPI)
#include <acpi/processor.h>
#endif

#define BYT_RATIOS 0x66a
#define BYT_VIDS 0x66b
#define BYT_TURBO_RATIOS 0x66c
Expand Down Expand Up @@ -117,9 +113,6 @@ struct cpudata {
u64 prev_mperf;
u64 prev_tsc;
struct sample sample;
#if IS_ENABLED(CONFIG_ACPI)
struct acpi_processor_performance acpi_perf_data;
#endif
};

static struct cpudata **all_cpu_data;
Expand Down Expand Up @@ -150,7 +143,6 @@ struct cpu_defaults {
static struct pstate_adjust_policy pid_params;
static struct pstate_funcs pstate_funcs;
static int hwp_active;
static int no_acpi_perf;

struct perf_limits {
int no_turbo;
Expand Down Expand Up @@ -197,153 +189,6 @@ static struct perf_limits *limits = &performance_limits;
static struct perf_limits *limits = &powersave_limits;
#endif

#if IS_ENABLED(CONFIG_ACPI)
/*
* The max target pstate ratio is a 8 bit value in both PLATFORM_INFO MSR and
* in TURBO_RATIO_LIMIT MSR, which pstate driver stores in max_pstate and
* max_turbo_pstate fields. The PERF_CTL MSR contains 16 bit value for P state
* ratio, out of it only high 8 bits are used. For example 0x1700 is setting
* target ratio 0x17. The _PSS control value stores in a format which can be
* directly written to PERF_CTL MSR. But in intel_pstate driver this shift
* occurs during write to PERF_CTL (E.g. for cores core_set_pstate()).
* This function converts the _PSS control value to intel pstate driver format
* for comparison and assignment.
*/
static int convert_to_native_pstate_format(struct cpudata *cpu, int index)
{
return cpu->acpi_perf_data.states[index].control >> 8;
}

static int intel_pstate_init_perf_limits(struct cpufreq_policy *policy)
{
struct cpudata *cpu;
int ret;
bool turbo_absent = false;
int max_pstate_index;
int min_pss_ctl, max_pss_ctl, turbo_pss_ctl;
int i;

cpu = all_cpu_data[policy->cpu];

pr_debug("intel_pstate: default limits 0x%x 0x%x 0x%x\n",
cpu->pstate.min_pstate, cpu->pstate.max_pstate,
cpu->pstate.turbo_pstate);

if (!cpu->acpi_perf_data.shared_cpu_map &&
zalloc_cpumask_var_node(&cpu->acpi_perf_data.shared_cpu_map,
GFP_KERNEL, cpu_to_node(policy->cpu))) {
return -ENOMEM;
}

ret = acpi_processor_register_performance(&cpu->acpi_perf_data,
policy->cpu);
if (ret)
return ret;

/*
* Check if the control value in _PSS is for PERF_CTL MSR, which should
* guarantee that the states returned by it map to the states in our
* list directly.
*/
if (cpu->acpi_perf_data.control_register.space_id !=
ACPI_ADR_SPACE_FIXED_HARDWARE)
return -EIO;

pr_debug("intel_pstate: CPU%u - ACPI _PSS perf data\n", policy->cpu);
for (i = 0; i < cpu->acpi_perf_data.state_count; i++)
pr_debug(" %cP%d: %u MHz, %u mW, 0x%x\n",
(i == cpu->acpi_perf_data.state ? '*' : ' '), i,
(u32) cpu->acpi_perf_data.states[i].core_frequency,
(u32) cpu->acpi_perf_data.states[i].power,
(u32) cpu->acpi_perf_data.states[i].control);

/*
* If there is only one entry _PSS, simply ignore _PSS and continue as
* usual without taking _PSS into account
*/
if (cpu->acpi_perf_data.state_count < 2)
return 0;

turbo_pss_ctl = convert_to_native_pstate_format(cpu, 0);
min_pss_ctl = convert_to_native_pstate_format(cpu,
cpu->acpi_perf_data.state_count - 1);
/* Check if there is a turbo freq in _PSS */
if (turbo_pss_ctl <= cpu->pstate.max_pstate &&
turbo_pss_ctl > cpu->pstate.min_pstate) {
pr_debug("intel_pstate: no turbo range exists in _PSS\n");
limits->no_turbo = limits->turbo_disabled = 1;
cpu->pstate.turbo_pstate = cpu->pstate.max_pstate;
turbo_absent = true;
}

/* Check if the max non turbo p state < Intel P state max */
max_pstate_index = turbo_absent ? 0 : 1;
max_pss_ctl = convert_to_native_pstate_format(cpu, max_pstate_index);
if (max_pss_ctl < cpu->pstate.max_pstate &&
max_pss_ctl > cpu->pstate.min_pstate)
cpu->pstate.max_pstate = max_pss_ctl;

/* check If min perf > Intel P State min */
if (min_pss_ctl > cpu->pstate.min_pstate &&
min_pss_ctl < cpu->pstate.max_pstate) {
cpu->pstate.min_pstate = min_pss_ctl;
policy->cpuinfo.min_freq = min_pss_ctl * cpu->pstate.scaling;
}

if (turbo_absent)
policy->cpuinfo.max_freq = cpu->pstate.max_pstate *
cpu->pstate.scaling;
else {
policy->cpuinfo.max_freq = cpu->pstate.turbo_pstate *
cpu->pstate.scaling;
/*
* The _PSS table doesn't contain whole turbo frequency range.
* This just contains +1 MHZ above the max non turbo frequency,
* with control value corresponding to max turbo ratio. But
* when cpufreq set policy is called, it will call with this
* max frequency, which will cause a reduced performance as
* this driver uses real max turbo frequency as the max
* frequeny. So correct this frequency in _PSS table to
* correct max turbo frequency based on the turbo ratio.
* Also need to convert to MHz as _PSS freq is in MHz.
*/
cpu->acpi_perf_data.states[0].core_frequency =
turbo_pss_ctl * 100;
}

pr_debug("intel_pstate: Updated limits using _PSS 0x%x 0x%x 0x%x\n",
cpu->pstate.min_pstate, cpu->pstate.max_pstate,
cpu->pstate.turbo_pstate);
pr_debug("intel_pstate: policy max_freq=%d Khz min_freq = %d KHz\n",
policy->cpuinfo.max_freq, policy->cpuinfo.min_freq);

return 0;
}

static int intel_pstate_exit_perf_limits(struct cpufreq_policy *policy)
{
struct cpudata *cpu;

if (!no_acpi_perf)
return 0;

cpu = all_cpu_data[policy->cpu];
acpi_processor_unregister_performance(policy->cpu);
return 0;
}

#else
static int intel_pstate_init_perf_limits(struct cpufreq_policy *policy)
{
return 0;
}

static int intel_pstate_exit_perf_limits(struct cpufreq_policy *policy)
{
return 0;
}
#endif

static inline void pid_reset(struct _pid *pid, int setpoint, int busy,
int deadband, int integral) {
pid->setpoint = setpoint;
Expand Down Expand Up @@ -1303,30 +1148,18 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
policy->cpuinfo.min_freq = cpu->pstate.min_pstate * cpu->pstate.scaling;
policy->cpuinfo.max_freq =
cpu->pstate.turbo_pstate * cpu->pstate.scaling;
if (!no_acpi_perf)
intel_pstate_init_perf_limits(policy);
/*
* If there is no acpi perf data or error, we ignore and use Intel P
* state calculated limits, So this is not fatal error.
*/
policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
cpumask_set_cpu(policy->cpu, policy->cpus);

return 0;
}

static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
{
return intel_pstate_exit_perf_limits(policy);
}

static struct cpufreq_driver intel_pstate_driver = {
.flags = CPUFREQ_CONST_LOOPS,
.verify = intel_pstate_verify_policy,
.setpolicy = intel_pstate_set_policy,
.get = intel_pstate_get,
.init = intel_pstate_cpu_init,
.exit = intel_pstate_cpu_exit,
.stop_cpu = intel_pstate_stop_cpu,
.name = "intel_pstate",
};
Expand Down Expand Up @@ -1368,6 +1201,7 @@ static void copy_cpu_funcs(struct pstate_funcs *funcs)
}

#if IS_ENABLED(CONFIG_ACPI)
#include <acpi/processor.h>

static bool intel_pstate_no_acpi_pss(void)
{
Expand Down Expand Up @@ -1563,9 +1397,6 @@ static int __init intel_pstate_setup(char *str)
force_load = 1;
if (!strcmp(str, "hwp_only"))
hwp_only = 1;
if (!strcmp(str, "no_acpi"))
no_acpi_perf = 1;

return 0;
}
early_param("intel_pstate", intel_pstate_setup);
Expand Down

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