Commit d06dde95 authored by Mario Limonciello's avatar Mario Limonciello Committed by Mario Limonciello
Browse files

ACPI / idle: override c-state latency when not in conformance with s0ix

Generally the C-state latency is provided by the _CST method or FADT but
some OEM platforms using AMD Picasso, Renoir, Van Gogh, and Cezanne set
the C2 latency greater than C3's which causes the C2 state to be skipped.
That will block the core entering PC6, which prevents s0ix working
properly on Linux systems.

In other operating systems the latency values are not validated and this
does not cause problems by skipping states.

To avoid this issue happening on Linux, detect when latencies are not an
arithmetic progression and sort them.

Link: 026d186e
Link: drm/amd#1230 (comment 712174)

Suggested-by: default avatarPrike Liang <>
Suggested-by: default avatarAlex Deucher <>
Signed-off-by: default avatarMario Limonciello <>
Change-Id: Ibf87933976385a263f8838296b01a7db2c9bc0d8
parent e03fca7d
......@@ -16,6 +16,7 @@
#include <linux/acpi.h>
#include <linux/dmi.h>
#include <linux/sched.h> /* need_resched() */
#include <linux/sort.h>
#include <linux/tick.h>
#include <linux/cpuidle.h>
#include <linux/cpu.h>
......@@ -387,10 +388,37 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
static int acpi_cst_latency_cmp(const void *a, const void *b)
const struct acpi_processor_cx *x = a, *y = b;
if (!(x->valid && y->valid))
return 0;
if (x->latency > y->latency)
return 1;
if (x->latency < y->latency)
return -1;
return 0;
static void acpi_cst_latency_swap(void *a, void *b, int n)
struct acpi_processor_cx *x = a, *y = b;
u32 tmp;
if (!(x->valid && y->valid))
tmp = x->latency;
x->latency = y->latency;
y->latency = tmp;
static int acpi_processor_power_verify(struct acpi_processor *pr)
unsigned int i;
unsigned int working = 0;
unsigned int last_latency = 0;
unsigned int last_type = 0;
bool buggy_latency = false;
pr->power.timer_broadcast_on_state = INT_MAX;
......@@ -414,12 +442,24 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
if (!cx->valid)
if (cx->type >= last_type && cx->latency < last_latency)
buggy_latency = true;
last_latency = cx->latency;
last_type = cx->type;
lapic_timer_check_state(i, pr, cx);
if (buggy_latency) {
pr_notice("FW issue: working around C-state latencies out of order\n");
sort(&pr->power.states[1], max_cstate,
sizeof(struct acpi_processor_cx),
return (working);
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