[N] [PATCH] intel_idle: Disable promotion to C1E on Jasper Lake and Elkhart Lake

[Kai-Heng Feng]

BugLink: https://bugs.launchpad.net/bugs/2077858

PCIe ethernet throughut is sub-optimal on Jasper Lake and Elkhart Lake.

The CPU can take long time to exit to C0 to handle IRQ and perform DMA
when C1E has been entered.

For this reason, adjust intel_idle to disable promotion to C1E and still
use C-states from ACPI _CST on those two platforms.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=219023
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
Link: https://patch.msgid.link/20240820041128.102452-1-kai.heng.feng@canonical.com
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
(backported from commit 5bb33212b5c664396e5de4cd5a2999abb84a3978 linux-next)
[khfeng: Adjusted for Intel CPU macro change]
Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
---
 drivers/idle/intel_idle.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index bcf1198e8991..67e018643345 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -1475,6 +1475,10 @@ static const struct idle_cpu idle_cpu_dnv __initconst = {
 	.use_acpi = true,
 };
 
+static const struct idle_cpu idle_cpu_tmt __initconst = {
+	.disable_promotion_to_c1e = true,
+};
+
 static const struct idle_cpu idle_cpu_snr __initconst = {
 	.state_table = snr_cstates,
 	.disable_promotion_to_c1e = true,
@@ -1538,6 +1542,8 @@ static const struct x86_cpu_id intel_idle_ids[] __initconst = {
 	X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT,	&idle_cpu_bxt),
 	X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT_PLUS,	&idle_cpu_bxt),
 	X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT_D,	&idle_cpu_dnv),
+	X86_MATCH_INTEL_FAM6_MODEL(ATOM_TREMONT,	&idle_cpu_tmt),
+	X86_MATCH_INTEL_FAM6_MODEL(ATOM_TREMONT_L,	&idle_cpu_tmt),
 	X86_MATCH_INTEL_FAM6_MODEL(ATOM_TREMONT_D,	&idle_cpu_snr),
 	X86_MATCH_INTEL_FAM6_MODEL(ATOM_CRESTMONT,	&idle_cpu_grr),
 	X86_MATCH_INTEL_FAM6_MODEL(ATOM_CRESTMONT_X,	&idle_cpu_srf),
@@ -2074,7 +2080,7 @@ static void __init intel_idle_cpuidle_driver_init(struct cpuidle_driver *drv)
 
 	drv->state_count = 1;
 
-	if (icpu)
+	if (icpu && icpu->state_table)
 		intel_idle_init_cstates_icpu(drv);
 	else
 		intel_idle_init_cstates_acpi(drv);
@@ -2208,7 +2214,11 @@ static int __init intel_idle_init(void)
 
 	icpu = (const struct idle_cpu *)id->driver_data;
 	if (icpu) {
-		cpuidle_state_table = icpu->state_table;
+		if (icpu->state_table)
+			cpuidle_state_table = icpu->state_table;
+		else if (!intel_idle_acpi_cst_extract())
+			return -ENODEV;
+
 		auto_demotion_disable_flags = icpu->auto_demotion_disable_flags;
 		if (icpu->disable_promotion_to_c1e)
 			c1e_promotion = C1E_PROMOTION_DISABLE;
-- 
2.43.0