[PATCH v2] ACPI: processor: Use Apple-specific methods for P/C-states

[PATCH v2] 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
as they include better P/C-States.
These methods are used in macOS (X86PlatformPlugin.kext),
and when not found we fallback to generic _PSS and _CST methods.

Changes in v2:
- Improved description of the patch
- Replaced goto's and if statement's with new functions
- Added support to differentiate _PSS and APSS in debug info/error info
- Added support to differentiate _CST and ACST in debug info/error info
- Used Package instead of variable for ACST description

Link to v1:
https://lore.kernel.org/all/20261015204450.1270-1-atharvatiwarilinuxdev@gmail.com/

Signed-off-by: Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
---
 drivers/acpi/acpi_processor.c    | 80 +++++++++++++++++++++-----------
 drivers/acpi/processor_perflib.c | 43 +++++++++++++----
 2 files changed, 86 insertions(+), 37 deletions(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 5fbab5417..bbe471b3c 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>
@@ -815,6 +816,22 @@ bool acpi_processor_claim_cst_control(void)
 }
 EXPORT_SYMBOL_NS_GPL(acpi_processor_claim_cst_control, "ACPI_PROCESSOR_IDLE");
 
+static int acpi_processor_apple_acst(acpi_handle handle, struct acpi_buffer *buffer)
+{
+	acpi_status status;
+
+	if (!x86_apple_machine)
+		return 0;
+
+	status = acpi_evaluate_object(handle, "ACST", NULL, buffer);
+	if (ACPI_FAILURE(status)) {
+		buffer->length = ACPI_ALLOCATE_BUFFER;
+		buffer->pointer = NULL;
+		return 0;
+	}
+
+	return 1;
+}
 /**
  * acpi_processor_evaluate_cst - Evaluate the processor _CST control method.
  * @handle: ACPI handle of the processor object containing the _CST.
@@ -837,28 +854,35 @@ 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;
+	bool using_acst = false;
 
-	status = acpi_evaluate_object(handle, "_CST", NULL, &buffer);
-	if (ACPI_FAILURE(status)) {
-		acpi_handle_debug(handle, "No _CST\n");
-		return -ENODEV;
+	using_acst = acpi_processor_apple_acst(handle, &buffer);
+	if (using_acst)
+		base = 1; /* ACST is a 4 field package we need to skip the first field */
+
+	if (!using_acst) {
+		status = acpi_evaluate_object(handle, "_CST", NULL, &buffer);
+		if (ACPI_FAILURE(status)) {
+			acpi_handle_debug(handle, "No _CST\n");
+			return -ENODEV;
+		}
 	}
 
 	cst = buffer.pointer;
 
-	/* There must be at least 2 elements. */
-	if (!cst || cst->type != ACPI_TYPE_PACKAGE || cst->package.count < 2) {
-		acpi_handle_warn(handle, "Invalid _CST output\n");
+	/* There must be at least 2 elements for _CST and at least 3 elements for ACST. */
+	if (!cst || cst->type != ACPI_TYPE_PACKAGE || cst->package.count < base + 2) {
+		acpi_handle_warn(handle, "Invalid %s output\n", using_acst ? "ACST" : "_CST");
 		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) {
-		acpi_handle_warn(handle, "Inconsistent _CST data\n");
+	if (count < 1 || count != cst->package.count - 1 - base) {
+		acpi_handle_warn(handle, "Inconsistent %s data\n", using_acst ? "ACST" : "_CST");
 		ret = -EFAULT;
 		goto end;
 	}
@@ -882,24 +906,24 @@ 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);
+			acpi_handle_info(handle, "%s C%d type(%x) is not package, skip...\n",
+					 using_acst ? "ACST" : "_CST", i, element->type);
 			continue;
 		}
 
 		if (element->package.count != 4) {
-			acpi_handle_info(handle, "_CST C%d package count(%d) is not 4, skip...\n",
-					 i, element->package.count);
+			acpi_handle_info(handle, "%s C%d package count(%d) is not 4, skip...\n",
+					 using_acst ? "ACST" : "_CST", i, element->package.count);
 			continue;
 		}
 
 		obj = &element->package.elements[0];
 
 		if (obj->type != ACPI_TYPE_BUFFER) {
-			acpi_handle_info(handle, "_CST C%d package element[0] type(%x) is not buffer, skip...\n",
-					 i, obj->type);
+			acpi_handle_info(handle, "%s C%d package element[0] type(%x) is not buffer, skip...\n",
+					 using_acst ? "ACST" : "_CST", i, obj->type);
 			continue;
 		}
 
@@ -907,8 +931,8 @@ int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
 
 		obj = &element->package.elements[1];
 		if (obj->type != ACPI_TYPE_INTEGER) {
-			acpi_handle_info(handle, "_CST C[%d] package element[1] type(%x) is not integer, skip...\n",
-					 i, obj->type);
+			acpi_handle_info(handle, "%s C[%d] package element[1] type(%x) is not integer, skip...\n",
+					 using_acst ? "ACST" : "_CST", i, obj->type);
 			continue;
 		}
 
@@ -947,8 +971,8 @@ int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
 				cx.entry_method = ACPI_CSTATE_HALT;
 				snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
 			} else {
-				acpi_handle_info(handle, "_CST C%d declares FIXED_HARDWARE C-state but not supported in hardware, skip...\n",
-						 i);
+				acpi_handle_info(handle, "%s C%d declares FIXED_HARDWARE C-state but not supported in hardware, skip...\n",
+						 using_acst ? "ACST" : "_CST", i);
 				continue;
 			}
 		} else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
@@ -956,8 +980,8 @@ int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
 			snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI IOPORT 0x%x",
 				 cx.address);
 		} else {
-			acpi_handle_info(handle, "_CST C%d space_id(%x) neither FIXED_HARDWARE nor SYSTEM_IO, skip...\n",
-					 i, reg->space_id);
+			acpi_handle_info(handle, "%s C%d space_id(%x) neither FIXED_HARDWARE nor SYSTEM_IO, skip...\n",
+					 using_acst ? "ACST" : "_CST", i, reg->space_id);
 			continue;
 		}
 
@@ -966,8 +990,8 @@ int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
 
 		obj = &element->package.elements[2];
 		if (obj->type != ACPI_TYPE_INTEGER) {
-			acpi_handle_info(handle, "_CST C%d package element[2] type(%x) not integer, skip...\n",
-					 i, obj->type);
+			acpi_handle_info(handle, "%s C%d package element[2] type(%x) not integer, skip...\n",
+					 using_acst ? "ACST" : "_CST", i, obj->type);
 			continue;
 		}
 
@@ -975,8 +999,8 @@ int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
 
 		obj = &element->package.elements[3];
 		if (obj->type != ACPI_TYPE_INTEGER) {
-			acpi_handle_info(handle, "_CST C%d package element[3] type(%x) not integer, skip...\n",
-					 i, obj->type);
+			acpi_handle_info(handle, "%s C%d package element[3] type(%x) not integer, skip...\n",
+					 using_acst ? "ACST" : "_CST", i, obj->type);
 			continue;
 		}
 
diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 9e25d6124..9b9533649 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>
@@ -313,6 +314,23 @@ static void amd_fixup_frequency(struct acpi_processor_px *px, int i)
 	}
 }
 
+static int acpi_evaluate_apple_apss(acpi_handle handle, struct acpi_buffer *buffer)
+{
+	acpi_status status;
+
+	if (!x86_apple_machine)
+		return 0;
+
+	status = acpi_evaluate_object(handle, "APSS", NULL, buffer);
+	if (ACPI_FAILURE(status)) {
+		buffer->length = ACPI_ALLOCATE_BUFFER;
+		buffer->pointer = NULL;
+		return 0;
+	}
+
+	return 1;
+}
+
 static int acpi_processor_get_performance_states(struct acpi_processor *pr)
 {
 	int result = 0;
@@ -323,16 +341,21 @@ static int acpi_processor_get_performance_states(struct acpi_processor *pr)
 	union acpi_object *pss = NULL;
 	int i;
 	int last_invalid = -1;
+	bool using_apss;
 
-	status = acpi_evaluate_object(pr->handle, "_PSS", NULL, &buffer);
-	if (ACPI_FAILURE(status)) {
-		acpi_evaluation_failure_warn(pr->handle, "_PSS", status);
-		return -ENODEV;
+	using_apss = acpi_evaluate_apple_apss(pr->handle, &buffer);
+
+	if (!using_apss) {
+		status = acpi_evaluate_object(pr->handle, "_PSS", NULL, &buffer);
+		if (ACPI_FAILURE(status)) {
+			acpi_evaluation_failure_warn(pr->handle, "_PSS", status);
+			return -ENODEV;
+		}
 	}
 
 	pss = buffer.pointer;
 	if (!pss || pss->type != ACPI_TYPE_PACKAGE) {
-		pr_err("Invalid _PSS data\n");
+		pr_err("Invalid %s data\n", using_apss ? "APSS" : "_PSS");
 		result = -EFAULT;
 		goto end;
 	}
@@ -360,7 +383,8 @@ static int acpi_processor_get_performance_states(struct acpi_processor *pr)
 		status = acpi_extract_package(&(pss->package.elements[i]),
 					      &format, &state);
 		if (ACPI_FAILURE(status)) {
-			acpi_handle_warn(pr->handle, "Invalid _PSS data: %s\n",
+			acpi_handle_warn(pr->handle, "Invalid %s data: %s\n",
+					 using_apss ? "APSS" : "_PSS",
 					 acpi_format_exception(status));
 			result = -EFAULT;
 			kfree(pr->performance->states);
@@ -384,8 +408,8 @@ static int acpi_processor_get_performance_states(struct acpi_processor *pr)
 		if (!px->core_frequency ||
 		    (u32)(px->core_frequency * 1000) != px->core_frequency * 1000) {
 			pr_err(FW_BUG
-			       "Invalid BIOS _PSS frequency found for processor %d: 0x%llx MHz\n",
-			       pr->id, px->core_frequency);
+			       "Invalid BIOS %s frequency found for processor %d: 0x%llx MHz\n",
+			       using_apss ? "APSS" : "_PSS", pr->id, px->core_frequency);
 			if (last_invalid == -1)
 				last_invalid = i;
 		} else {
@@ -402,7 +426,8 @@ static int acpi_processor_get_performance_states(struct acpi_processor *pr)
 
 	if (last_invalid == 0) {
 		pr_err(FW_BUG
-			   "No valid BIOS _PSS frequency found for processor %d\n", pr->id);
+			   "No valid BIOS %s frequency found for processor %d\n",
+			   using_apss ? "APSS" : "_PSS",  pr->id);
 		result = -EFAULT;
 		kfree(pr->performance->states);
 		pr->performance->states = NULL;
-- 
2.55.0