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Subject[PATCH] cpufreq: intel_pstate: enable HWP before manipulating on corresponding registers
Date
The following warning was triggered after resumed from S3 -
if all the nonboot CPUs were put offline before suspend:

[ 1840.329515] unchecked MSR access error: RDMSR from 0x771 at rIP: 0xffffffff86061e3a (native_read_msr+0xa/0x30)
[ 1840.329516] Call Trace:
[ 1840.329521] __rdmsr_on_cpu+0x33/0x50
[ 1840.329525] generic_exec_single+0x81/0xb0
[ 1840.329527] smp_call_function_single+0xd2/0x100
[ 1840.329530] ? acpi_ds_result_pop+0xdd/0xf2
[ 1840.329532] ? acpi_ds_create_operand+0x215/0x23c
[ 1840.329534] rdmsrl_on_cpu+0x57/0x80
[ 1840.329536] ? cpumask_next+0x1b/0x20
[ 1840.329538] ? rdmsrl_on_cpu+0x57/0x80
[ 1840.329541] intel_pstate_update_perf_limits+0xf3/0x220
[ 1840.329544] ? notifier_call_chain+0x4a/0x70
[ 1840.329546] intel_pstate_set_policy+0x4e/0x150
[ 1840.329548] cpufreq_set_policy+0xcd/0x2f0
[ 1840.329550] cpufreq_update_policy+0xb2/0x130
[ 1840.329552] ? cpufreq_update_policy+0x130/0x130
[ 1840.329556] acpi_processor_ppc_has_changed+0x65/0x80
[ 1840.329558] acpi_processor_notify+0x80/0x100
[ 1840.329561] acpi_ev_notify_dispatch+0x44/0x5c
[ 1840.329563] acpi_os_execute_deferred+0x14/0x20
[ 1840.329565] process_one_work+0x193/0x3c0
[ 1840.329567] worker_thread+0x35/0x3b0
[ 1840.329569] kthread+0x125/0x140
[ 1840.329571] ? process_one_work+0x3c0/0x3c0
[ 1840.329572] ? kthread_park+0x60/0x60
[ 1840.329575] ? do_syscall_64+0x67/0x180
[ 1840.329577] ret_from_fork+0x25/0x30
[ 1840.329585] unchecked MSR access error: WRMSR to 0x774 (tried to write 0x0000000000000000) at rIP: 0xffffffff86061f78 (native_write_msr+0x8/0x30)
[ 1840.329586] Call Trace:
[ 1840.329587] __wrmsr_on_cpu+0x37/0x40
[ 1840.329589] generic_exec_single+0x81/0xb0
[ 1840.329592] smp_call_function_single+0xd2/0x100
[ 1840.329594] ? acpi_ds_create_operand+0x215/0x23c
[ 1840.329595] ? cpumask_next+0x1b/0x20
[ 1840.329597] wrmsrl_on_cpu+0x57/0x70
[ 1840.329598] ? rdmsrl_on_cpu+0x57/0x80
[ 1840.329599] ? wrmsrl_on_cpu+0x57/0x70
[ 1840.329602] intel_pstate_hwp_set+0xd3/0x150
[ 1840.329604] intel_pstate_set_policy+0x119/0x150
[ 1840.329606] cpufreq_set_policy+0xcd/0x2f0
[ 1840.329607] cpufreq_update_policy+0xb2/0x130
[ 1840.329610] ? cpufreq_update_policy+0x130/0x130
[ 1840.329613] acpi_processor_ppc_has_changed+0x65/0x80
[ 1840.329615] acpi_processor_notify+0x80/0x100
[ 1840.329617] acpi_ev_notify_dispatch+0x44/0x5c
[ 1840.329619] acpi_os_execute_deferred+0x14/0x20
[ 1840.329620] process_one_work+0x193/0x3c0
[ 1840.329622] worker_thread+0x35/0x3b0
[ 1840.329624] kthread+0x125/0x140
[ 1840.329625] ? process_one_work+0x3c0/0x3c0
[ 1840.329626] ? kthread_park+0x60/0x60
[ 1840.329628] ? do_syscall_64+0x67/0x180
[ 1840.329631] ret_from_fork+0x25/0x30

This is because if there's only one online CPU, the MSR_PM_ENABLE
(package wide)can not be enabled after resumed, due to
intel_pstate_hwp_enable() will only be invoked on AP's online
process after resumed - if there's no AP online, the HWP remains
disabled after resumed (BIOS has disabled it in S3).

The re-enabling of HWP can not be put into intel_pstate_resume()
as it is too late according to the log above. It is applicable
to do it in syscore_resume() but this requires a new notifier.
Thus forcely enable the HWP before manipulating on them, and this
should not impact much because users seldom touch HWP registers.

Reported-by: Doug Smythies <dsmythies@telus.net>
Signed-off-by: Yu Chen <yu.c.chen@intel.com>
---
drivers/cpufreq/intel_pstate.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 93a0e88bef76..b808f0127192 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -689,6 +689,8 @@ static void intel_pstate_get_hwp_max(unsigned int cpu, int *phy_max,
{
u64 cap;

+ /* In case HWP is disabled after resumed from S3. */
+ wrmsrl_on_cpu(cpu, MSR_PM_ENABLE, 0x1);
rdmsrl_on_cpu(cpu, MSR_HWP_CAPABILITIES, &cap);
if (global.no_turbo)
*current_max = HWP_GUARANTEED_PERF(cap);
@@ -711,6 +713,8 @@ static void intel_pstate_hwp_set(unsigned int cpu)
if (cpu_data->policy == CPUFREQ_POLICY_PERFORMANCE)
min = max;

+ /* In case HWP is disabled after resumed from S3. */
+ wrmsrl_on_cpu(cpu, MSR_PM_ENABLE, 0x1);
rdmsrl_on_cpu(cpu, MSR_HWP_REQUEST, &value);

value &= ~HWP_MIN_PERF(~0L);
--
2.13.6
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