[PATCH RESEND] ACPI: processor: Use Apple-specific methods for P/C-states

[PATCH RESEND] ACPI: processor: Use Apple-specific methods for P/C-states

[Atharva Tiwari]

Use APSS and ACST instead of _PSS and _CST when available on Intel Macs.
These methods are used in X86PlatformPlugin.kext, and when not found we
fallback to generic _PSS and _CST methods.

Signed-off-by: Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
---
 drivers/acpi/acpi_processor.c    | 22 +++++++++++++++++-----
 drivers/acpi/processor_perflib.c | 10 ++++++++++
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 5fbab5417..782676ef7 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -18,6 +18,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/pci.h>
+#include <linux/platform_data/x86/apple.h>
 #include <linux/platform_device.h>
 
 #include <acpi/processor.h>
@@ -837,27 +838,38 @@ int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
 	acpi_status status;
 	u64 count;
 	int last_index = 0;
-	int i, ret = 0;
+	int i, ret = 0, base = 0;
 
+	if (x86_apple_machine) {
+		status = acpi_evaluate_object(handle, "ACST", NULL, &buffer);
+		if (ACPI_SUCCESS(status)) {
+			base = 1; /* ACST is a 4 field variable we need to skip the first field */
+			goto success;
+		}
+
+		buffer.length = ACPI_ALLOCATE_BUFFER;
+		buffer.pointer = NULL;
+	}
 	status = acpi_evaluate_object(handle, "_CST", NULL, &buffer);
 	if (ACPI_FAILURE(status)) {
 		acpi_handle_debug(handle, "No _CST\n");
 		return -ENODEV;
 	}
+success:
 
 	cst = buffer.pointer;
 
 	/* There must be at least 2 elements. */
-	if (!cst || cst->type != ACPI_TYPE_PACKAGE || cst->package.count < 2) {
+	if (!cst || cst->type != ACPI_TYPE_PACKAGE || cst->package.count < base + 2) {
 		acpi_handle_warn(handle, "Invalid _CST output\n");
 		ret = -EFAULT;
 		goto end;
 	}
 
-	count = cst->package.elements[0].integer.value;
+	count = cst->package.elements[base].integer.value;
 
 	/* Validate the number of C-states. */
-	if (count < 1 || count != cst->package.count - 1) {
+	if (count < 1 || count != cst->package.count - 1 - base) {
 		acpi_handle_warn(handle, "Inconsistent _CST data\n");
 		ret = -EFAULT;
 		goto end;
@@ -882,7 +894,7 @@ int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
 
 		memset(&cx, 0, sizeof(cx));
 
-		element = &cst->package.elements[i];
+		element = &cst->package.elements[base + i];
 		if (element->type != ACPI_TYPE_PACKAGE) {
 			acpi_handle_info(handle, "_CST C%d type(%x) is not package, skip...\n",
 					 i, element->type);
diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 9e25d6124..b4b36e60d 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -17,6 +17,7 @@
 #include <linux/cpufreq.h>
 #include <linux/slab.h>
 #include <linux/acpi.h>
+#include <linux/platform_data/x86/apple.h>
 #include <acpi/processor.h>
 #ifdef CONFIG_X86
 #include <asm/cpufeature.h>
@@ -324,11 +325,20 @@ static int acpi_processor_get_performance_states(struct acpi_processor *pr)
 	int i;
 	int last_invalid = -1;
 
+	if (x86_apple_machine) {
+		status = acpi_evaluate_object(pr->handle, "APSS", NULL, &buffer);
+		if (ACPI_SUCCESS(status))
+			goto success;
+
+		buffer.length = ACPI_ALLOCATE_BUFFER;
+		buffer.pointer = NULL;
+	}
 	status = acpi_evaluate_object(pr->handle, "_PSS", NULL, &buffer);
 	if (ACPI_FAILURE(status)) {
 		acpi_evaluation_failure_warn(pr->handle, "_PSS", status);
 		return -ENODEV;
 	}
+success:
 
 	pss = buffer.pointer;
 	if (!pss || pss->type != ACPI_TYPE_PACKAGE) {
-- 
2.55.0

Re: [PATCH RESEND] ACPI: processor: Use Apple-specific methods for P/C-states

[Atharva Tiwari]

Hi can i please get a update on this, i sent this patch almost 15 days
ago.

Thanks.

Re: [PATCH RESEND] ACPI: processor: Use Apple-specific methods for P/C-states

[Rafael J. Wysocki (Intel)]

On Thu, Oct 29, 2026 at 4:11 PM Atharva Tiwari
<atharvatiwarilinuxdev@gmail.com> wrote:
>
> Hi can i please get a update on this, i sent this patch almost 15 days
> ago.

You haven't provided a motivation for the change and I know nothing
about Apple platforms, sorry.

Re: [PATCH RESEND] ACPI: processor: Use Apple-specific methods for P/C-states

[Atharva Tiwari]

> You haven't provided a motivation for the change and I know nothing
> about Apple platforms, sorry.

APSS provides more P-states than _PSS on apple macs, for example on MacBookPro11,3

_PSS provides 17 P-states ranging from 800Mhz to 2301 Mhz, while
APSS provides 28 P-states ranging from 800Mhz to 3500 Mhz

Same with ACST, on Xserve3,1 _CST provides 2 C-states (C1, C6)
while ACST provides 3 C-states (C1, C2, C6).

This is also used in older macs only (before 2015).

And also macOS uses these.