drivers/intel/gma/acpi: Reduce display switching stubs

_DCS, _DGS and _DSS are required by specification. However,
we never implemented them properly, and no OS driver com-
plained yet. So we stub them out and keep the traditional
behavior in case an OS driver checks for their existence.

The old implementations also only returned static values as
there never was any write to their GNVS variables. The TRAP()
that was called in one place is actually implemented by some
ThinkPad's SMI handler as docking event. However, as the call
precedes these SMI handlers in coreboot history, it's most
likely an accident.

Change-Id: Ib0b9fcdd58df254d3b2290900e3bc206a7abd92d
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39726
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/drivers/intel/gma/acpi.c

@@ -102,39 +102,38 @@ drivers_intel_gma_displays_ssdt_generate(const struct i915_gpu_controller_info *
 		}
 
 		/*
-		Method(_DCS, 0)
+		 * _DCS, _DGS and _DSS are required by specification. However,
-		{
+		 * we never implemented them properly, and no OS driver com-
-			Return (^^XDCS(<device number>))
+		 * plained yet. So we stub them out and keep the traditional
-		}
+		 * behavior in case an OS driver checks for their existence.
+		 */
+
+		/*
+		  Method(_DCS, 0)
+		  {
+			Return (0x1d)
+		  }
 		*/
 		acpigen_write_method("_DCS", 0);
-		acpigen_emit_byte(0xa4); /* ReturnOp.  */
+		acpigen_write_return_integer(0x1d);
-		acpigen_emit_namestring("^^XDCS");
-		acpigen_write_byte(i);
 		acpigen_pop_len();
 
 		/*
-		Method(_DGS, 0)
+		  Method(_DGS, 0)
-		{
+		  {
-			Return (^^XDGS(<device number>))
+			Return (0)
-		}
+		  }
 		*/
 		acpigen_write_method("_DGS", 0);
-		acpigen_emit_byte(0xa4); /* ReturnOp.  */
+		acpigen_write_return_integer(0);
-		acpigen_emit_namestring("^^XDGS");
-		acpigen_write_byte(i);
 		acpigen_pop_len();
 
 		/*
-		Method(_DSS, 1)
+		  Method(_DSS, 1)
-		{
+		  {
-			^^XDSS(0x5a, Arg0)
+		  }
-		}
 		*/
 		acpigen_write_method("_DSS", 1);
-		acpigen_emit_namestring("^^XDSS");
-		acpigen_write_byte(i);
-		acpigen_emit_byte(0x68); /* Arg0Op.  */
 		acpigen_pop_len();
 
 		acpigen_pop_len();

src/drivers/intel/gma/acpi/common.asl

@@ -35,11 +35,6 @@
 	/* Display Output Switching */
 	Method (_DOS, 1)
 	{
-		/* Windows 2000 and Windows XP call _DOS to enable/disable
-		 * Display Output Switching during init and while a switch
-		 * is already active
-		 */
-		Store (And(Arg0, 7), DSEN)
 	}
 
 	/*
@@ -80,33 +75,3 @@
 			XBCM (DerefOf (Index (BRIG, Local0)))
 		}
 	}
-
-	/* Device Current Status */
-	Method(XDCS, 1)
-	{
-		TRAP(1)
-		If (And(CSTE, ShiftLeft (1, Arg0))) {
-			Return (0x1f)
-		}
-		Return(0x1d)
-	}
-
-	/* Query Device Graphics State */
-	Method(XDGS, 1)
-	{
-		If (And(NSTE, ShiftLeft (1, Arg0))) {
-			Return(1)
-		}
-		Return(0)
-	}
-
-	/* Device Set State */
-	Method(XDSS, 1)
-	{
-		/* If Parameter Arg0 is (1 << 31) | (1 << 30), the
-		 * display switch was completed
-		 */
-		If (LEqual(And(Arg0, 0xc0000000), 0xc0000000)) {
-			Store (NSTE, CSTE)
-		}
-	}

src/mainboard/51nb/x210/dsdt.asl

@@ -12,8 +12,6 @@ DefinitionBlock(
 	0x20110725	// OEM revision
 )
 {
-	Name(\DSEN, 1)
-
 	#include "acpi/platform.asl"
 
 	#include <soc/intel/skylake/acpi/globalnvs.asl>

src/southbridge/intel/bd82x6x/acpi/globalnvs.asl

@@ -16,7 +16,6 @@
 /* Global Variables */
 
 Name(\PICM, 0)		// IOAPIC/8259
-Name(\DSEN, 1)		// Display Output Switching Enable
 
 /* Global ACPI memory region. This region is used for passing information
  * between coreboot (aka "the system bios"), ACPI, and the SMI handler.
@@ -89,9 +88,6 @@ Field (GNVS, ByteAcc, NoLock, Preserve)
 	TLST,	 8,	// 0x3d - Display Toggle List pointer
 	CADL,	 8,	// 0x3e - Currently Attached Devices List
 	PADL,	 8,	// 0x3f - Previously Attached Devices List
-	CSTE,	16,	// 0x40 - Current display state
-	NSTE,	16,	// 0x42 - Next display state
-	SSTE,	16,	// 0x44 - Set display state
 	Offset (0x46),
 	NDID,	 8,	// 0x46 - Number of Device IDs
 	DID1,	32,	// 0x47 - Device ID 1

src/southbridge/intel/bd82x6x/nvs.h

@@ -75,9 +75,7 @@ typedef struct global_nvs_t {
 	u8	tlst; /* 0x3d - Display Toggle List Pointer */
 	u8	cadl; /* 0x3e - currently attached devices */
 	u8	padl; /* 0x3f - previously attached devices */
-	u16	cste; /* 0x40 - current display state */
+	u16	rsvd14[3];
-	u16	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];

src/southbridge/intel/i82801dx/nvs.h

@@ -69,9 +69,7 @@ typedef struct {
 	u8	tlst; /* 0x3d - Display Toggle List Pointer */
 	u8	cadl; /* 0x3e - currently attached devices */
 	u8	padl; /* 0x3f - previously attached devices */
-	u16	cste; /* 0x40 - current display state */
+	u16	rsvd14[3];
-	u16	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];

src/southbridge/intel/i82801gx/acpi/globalnvs.asl

@@ -16,7 +16,6 @@
 /* Global Variables */
 
 Name(\PICM, 0)		// IOAPIC/8259
-Name(\DSEN, 1)		// Display Output Switching Enable
 
 /* Global ACPI memory region. This region is used for passing information
  * between coreboot (aka "the system bios"), ACPI, and the SMI handler.
@@ -88,9 +87,7 @@ Field (GNVS, ByteAcc, NoLock, Preserve)
 	TLST,	 8,	// 0x3d - Display Toggle List pointer
 	CADL,	 8,	// 0x3e - Currently Attached Devices List
 	PADL,	 8,	// 0x3f - Previously Attached Devices List
-	CSTE,	16,	// 0x40 - Current display state
+	Offset (0x46),
-	NSTE,	16,	// 0x42 - Next display state
-	SSTE,	16,	// 0x44 - Set display state
 	NDID,	 8,	// 0x46 - Number of Device IDs
 	DID1,	32,	// 0x47 - Device ID 1
 	DID2,	32,	// 0x4b - Device ID 2

src/southbridge/intel/i82801gx/nvs.h

@@ -71,9 +71,7 @@ typedef struct {
 	u8	tlst; /* 0x3d - Display Toggle List Pointer */
 	u8	cadl; /* 0x3e - currently attached devices */
 	u8	padl; /* 0x3f - previously attached devices */
-	u16	cste; /* 0x40 - current display state */
+	u16	rsvd14[3];
-	u16	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];

src/southbridge/intel/i82801ix/acpi/globalnvs.asl

@@ -16,7 +16,6 @@
 /* Global Variables */
 
 Name(\PICM, 0)		// IOAPIC/8259
-Name(\DSEN, 1)		// Display Output Switching Enable
 
 /* Global ACPI memory region. This region is used for passing information
  * between coreboot (aka "the system bios"), ACPI, and the SMI handler.
@@ -92,9 +91,6 @@ Field (GNVS, ByteAcc, NoLock, Preserve)
 	TLST,	 8,	// 0x3d - Display Toggle List pointer
 	CADL,	 8,	// 0x3e - Currently Attached Devices List
 	PADL,	 8,	// 0x3f - Previously Attached Devices List
-	CSTE,	16,	// 0x40 - Current display state
-	NSTE,	16,	// 0x42 - Next display state
-	SSTE,	16,	// 0x44 - Set display state
 	Offset (0x46),
 	NDID,	 8,	// 0x46 - Number of Device IDs
 	DID1,	32,	// 0x47 - Device ID 1

src/southbridge/intel/i82801ix/nvs.h

@@ -73,9 +73,7 @@ typedef struct {
 	u8	tlst; /* 0x3d - Display Toggle List Pointer */
 	u8	cadl; /* 0x3e - currently attached devices */
 	u8	padl; /* 0x3f - previously attached devices */
-	u16	cste; /* 0x40 - current display state */
+	u16	rsvd14[3];
-	u16	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];

src/southbridge/intel/i82801jx/acpi/globalnvs.asl

@@ -16,7 +16,6 @@
 /* Global Variables */
 
 Name(\PICM, 0)		// IOAPIC/8259
-Name(\DSEN, 1)		// Display Output Switching Enable
 
 /* Global ACPI memory region. This region is used for passing information
  * between coreboot (aka "the system bios"), ACPI, and the SMI handler.
@@ -92,9 +91,6 @@ Field (GNVS, ByteAcc, NoLock, Preserve)
 	TLST,	 8,	// 0x3d - Display Toggle List pointer
 	CADL,	 8,	// 0x3e - Currently Attached Devices List
 	PADL,	 8,	// 0x3f - Previously Attached Devices List
-	CSTE,	16,	// 0x40 - Current display state
-	NSTE,	16,	// 0x42 - Next display state
-	SSTE,	16,	// 0x44 - Set display state
 	Offset (0x46),
 	NDID,	 8,	// 0x46 - Number of Device IDs
 	DID1,	32,	// 0x47 - Device ID 1

src/southbridge/intel/i82801jx/nvs.h

@@ -71,9 +71,7 @@ typedef struct {
 	u8	tlst; /* 0x3d - Display Toggle List Pointer */
 	u8	cadl; /* 0x3e - currently attached devices */
 	u8	padl; /* 0x3f - previously attached devices */
-	u16	cste; /* 0x40 - current display state */
+	u16	rsvd14[3];
-	u16	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];

src/southbridge/intel/ibexpeak/nvs.h

@@ -74,9 +74,7 @@ typedef struct global_nvs_t {
 	u8	tlst; /* 0x3d - Display Toggle List Pointer */
 	u8	cadl; /* 0x3e - currently attached devices */
 	u8	padl; /* 0x3f - previously attached devices */
-	u16	cste; /* 0x40 - current display state */
+	u16	rsvd14[3];
-	u16	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];

src/southbridge/intel/lynxpoint/acpi/globalnvs.asl

@@ -16,7 +16,6 @@
 /* Global Variables */
 
 Name(\PICM, 0)		// IOAPIC/8259
-Name(\DSEN, 1)		// Display Output Switching Enable
 
 /* Global ACPI memory region. This region is used for passing information
  * between coreboot (aka "the system bios"), ACPI, and the SMI handler.
@@ -89,9 +88,6 @@ Field (GNVS, ByteAcc, NoLock, Preserve)
 	TLST,	 8,	// 0x3d - Display Toggle List pointer
 	CADL,	 8,	// 0x3e - Currently Attached Devices List
 	PADL,	 8,	// 0x3f - Previously Attached Devices List
-	CSTE,	16,	// 0x40 - Current display state
-	NSTE,	16,	// 0x42 - Next display state
-	SSTE,	16,	// 0x44 - Set display state
 	Offset (0x46),
 	NDID,	 8,	// 0x46 - Number of Device IDs
 	DID1,	32,	// 0x47 - Device ID 1

src/southbridge/intel/lynxpoint/nvs.h

@@ -75,9 +75,7 @@ typedef struct global_nvs_t {
 	u8	tlst; /* 0x3d - Display Toggle List Pointer */
 	u8	cadl; /* 0x3e - currently attached devices */
 	u8	padl; /* 0x3f - previously attached devices */
-	u16	cste; /* 0x40 - current display state */
+	u16	rsvd14[3];
-	u16	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	/* TPM support */