intel_idle: Customize IceLake server support

On ICX platform, the C1E auto-promotion is enabled by default.
As a result, the CPU might fall into C1E more offen than previous
platforms. Besides, the C1E is not exposed to sysfs on ICX, which
is inconsistent with previous server platforms.

So disable C1E auto-promotion and expose C1E as a separate idle
state, so the C1E and C6 can be disabled via sysfs when necessary.

Beside C1 and C1E, the exit latency of C6 was measured
by a dedicated tool. However the exit latency(41us) exposed
by _CST is much smaller than the one we measured(128us). This
is probably due to the _CST uses the exit latency when woken
up from PC0+C6, rather than PC6+C6 when C6 was measured. Choose
the latter as we need the longest latency in theory.

Reported-by: kernel test robot <[email protected]>
Tested-by: Artem Bityutskiy <[email protected]>
Acked-by: Artem Bityutskiy <[email protected]>
Reviewed-by: Zhang Rui <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: yu-chen-surf

drivers/idle/intel_idle.c

@@ -752,6 +752,35 @@ static struct cpuidle_state skx_cstates[] __initdata = {
 		.enter = NULL }
 };
 
+static struct cpuidle_state icx_cstates[] __initdata = {
+	{
+		.name = "C1",
+		.desc = "MWAIT 0x00",
+		.flags = MWAIT2flg(0x00),
+		.exit_latency = 1,
+		.target_residency = 1,
+		.enter = &intel_idle,
+		.enter_s2idle = intel_idle_s2idle, },
+	{
+		.name = "C1E",
+		.desc = "MWAIT 0x01",
+		.flags = MWAIT2flg(0x01) | CPUIDLE_FLAG_ALWAYS_ENABLE,
+		.exit_latency = 4,
+		.target_residency = 4,
+		.enter = &intel_idle,
+		.enter_s2idle = intel_idle_s2idle, },
+	{
+		.name = "C6",
+		.desc = "MWAIT 0x20",
+		.flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
+		.exit_latency = 128,
+		.target_residency = 384,
+		.enter = &intel_idle,
+		.enter_s2idle = intel_idle_s2idle, },
+	{
+		.enter = NULL }
+};
+
 static struct cpuidle_state atom_cstates[] __initdata = {
 	{
 		.name = "C1E",
@@ -1056,6 +1085,12 @@ static const struct idle_cpu idle_cpu_skx __initconst = {
 	.use_acpi = true,
 };
 
+static const struct idle_cpu idle_cpu_icx __initconst = {
+	.state_table = icx_cstates,
+	.disable_promotion_to_c1e = true,
+	.use_acpi = true,
+};
+
 static const struct idle_cpu idle_cpu_avn __initconst = {
 	.state_table = avn_cstates,
 	.disable_promotion_to_c1e = true,
@@ -1110,6 +1145,7 @@ static const struct x86_cpu_id intel_idle_ids[] __initconst = {
 	X86_MATCH_INTEL_FAM6_MODEL(KABYLAKE_L,		&idle_cpu_skl),
 	X86_MATCH_INTEL_FAM6_MODEL(KABYLAKE,		&idle_cpu_skl),
 	X86_MATCH_INTEL_FAM6_MODEL(SKYLAKE_X,		&idle_cpu_skx),
+	X86_MATCH_INTEL_FAM6_MODEL(ICELAKE_X,		&idle_cpu_icx),
 	X86_MATCH_INTEL_FAM6_MODEL(XEON_PHI_KNL,	&idle_cpu_knl),
 	X86_MATCH_INTEL_FAM6_MODEL(XEON_PHI_KNM,	&idle_cpu_knl),
 	X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT,	&idle_cpu_bxt),