[PATCH 1/2] drm/amd: Disallow s0ix without BIOS support again

[Mario Limonciello]

commit cf488dcd0ab7 ("drm/amd: Allow s0ix without BIOS support") showed
improvements to power consumption over suspend when s0ix wasn't enabled in
BIOS and the system didn't support S3.

This patch however was misguided because the reason the system didn't
support S3 was because SMT was disabled in OEM BIOS setup.
This prevented the BIOS from allowing S3.

Also allowing GPUs to use the s2idle path actually causes problems if
they're invoked on systems that may not support s2idle in the platform
firmware. `systemd` has a tendency to try to use `s2idle` if `deep` fails
for any reason, which could lead to unexpected flows.

To make this the behavior discoverable and expected, revert commit
cf488dcd0ab7 ("drm/amd: Allow s0ix without BIOS support") and offer
a message if SMT appears to be disabled.

Cc: Rafael Ávila de Espíndola <rafael at espindo.la>
Link: https://github.com/torvalds/linux/blob/v6.1/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c#L1060
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2599
Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index 3a6b2e2089f6..a3523d03d769 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -28,6 +28,7 @@
 #include <linux/xarray.h>
 #include <linux/power_supply.h>
 #include <linux/pm_runtime.h>
+#include <linux/sched/smt.h>
 #include <linux/suspend.h>
 #include <acpi/video.h>
 #include <acpi/actbl.h>
@@ -1473,6 +1474,13 @@ void amdgpu_acpi_release(void)
  */
 bool amdgpu_acpi_is_s3_active(struct amdgpu_device *adev)
 {
+#ifdef CONFIG_X86
+	if (!sched_smt_active()) {
+		dev_warn_once(adev->dev,
+			      "SMT is disabled by the BIOS.\n"
+			      "To use suspend-to-ram enable SMT in BIOS setup.\n");
+	}
+#endif
 	return !(adev->flags & AMD_IS_APU) ||
 		(pm_suspend_target_state == PM_SUSPEND_MEM);
 }
@@ -1499,16 +1507,20 @@ bool amdgpu_acpi_is_s0ix_active(struct amdgpu_device *adev)
 	 * S0ix even though the system is suspending to idle, so return false
 	 * in that case.
 	 */
-	if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
+	if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)) {
 		dev_warn_once(adev->dev,
 			      "Power consumption will be higher as BIOS has not been configured for suspend-to-idle.\n"
 			      "To use suspend-to-idle change the sleep mode in BIOS setup.\n");
+		return false;
+	}
 
 #if !IS_ENABLED(CONFIG_AMD_PMC)
 	dev_warn_once(adev->dev,
 		      "Power consumption will be higher as the kernel has not been compiled with CONFIG_AMD_PMC.\n");
-#endif /* CONFIG_AMD_PMC */
+	return false;
+#else
 	return true;
+#endif /* CONFIG_AMD_PMC */
 }
 
 #endif /* CONFIG_SUSPEND */
-- 
2.34.1