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>

15 files changed, 28 insertions, 99 deletions

diff --git a/src/drivers/intel/gma/acpi.c b/src/drivers/intel/gma/acpi.c
index 3f71a5ea84..d3fb69dec8 100644
--- a/src/drivers/intel/gma/acpi.c
+++ b/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)
-		{
-			Return (^^XDCS(<device number>))
-		}
+		 * _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.
+		 */
+
+		/*
+		  Method(_DCS, 0)
+		  {
+			Return (0x1d)
+		  }
 		*/
 		acpigen_write_method("_DCS", 0);
-		acpigen_emit_byte(0xa4); /* ReturnOp.  */
-		acpigen_emit_namestring("^^XDCS");
-		acpigen_write_byte(i);
+		acpigen_write_return_integer(0x1d);
 		acpigen_pop_len();
 
 		/*
-		Method(_DGS, 0)
-		{
-			Return (^^XDGS(<device number>))
-		}
+		  Method(_DGS, 0)
+		  {
+			Return (0)
+		  }
 		*/
 		acpigen_write_method("_DGS", 0);
-		acpigen_emit_byte(0xa4); /* ReturnOp.  */
-		acpigen_emit_namestring("^^XDGS");
-		acpigen_write_byte(i);
+		acpigen_write_return_integer(0);
 		acpigen_pop_len();
 
 		/*
-		Method(_DSS, 1)
-		{
-			^^XDSS(0x5a, Arg0)
-		}
+		  Method(_DSS, 1)
+		  {
+		  }
 		*/
 		acpigen_write_method("_DSS", 1);
-		acpigen_emit_namestring("^^XDSS");
-		acpigen_write_byte(i);
-		acpigen_emit_byte(0x68); /* Arg0Op.  */
 		acpigen_pop_len();
 
 		acpigen_pop_len();
diff --git a/src/drivers/intel/gma/acpi/common.asl b/src/drivers/intel/gma/acpi/common.asl
index 3932a88e87..09d48a20e0 100644
--- a/src/drivers/intel/gma/acpi/common.asl
+++ b/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)
-		}
-	}
diff --git a/src/mainboard/51nb/x210/dsdt.asl b/src/mainboard/51nb/x210/dsdt.asl
index 441a80dd4a..b88a56c632 100644
--- a/src/mainboard/51nb/x210/dsdt.asl
+++ b/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>
diff --git a/src/southbridge/intel/bd82x6x/acpi/globalnvs.asl b/src/southbridge/intel/bd82x6x/acpi/globalnvs.asl
index 3e7874cfaa..1b23cef6ac 100644
--- a/src/southbridge/intel/bd82x6x/acpi/globalnvs.asl
+++ b/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
diff --git a/src/southbridge/intel/bd82x6x/nvs.h b/src/southbridge/intel/bd82x6x/nvs.h
index 326c2ea0d5..93ebed66ec 100644
--- a/src/southbridge/intel/bd82x6x/nvs.h
+++ b/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	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
+	u16	rsvd14[3];
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];
diff --git a/src/southbridge/intel/i82801dx/nvs.h b/src/southbridge/intel/i82801dx/nvs.h
index b95f9c95fa..1882fcb26c 100644
--- a/src/southbridge/intel/i82801dx/nvs.h
+++ b/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	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
+	u16	rsvd14[3];
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];
diff --git a/src/southbridge/intel/i82801gx/acpi/globalnvs.asl b/src/southbridge/intel/i82801gx/acpi/globalnvs.asl
index 5787cec5c2..4a19de1476 100644
--- a/src/southbridge/intel/i82801gx/acpi/globalnvs.asl
+++ b/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
-	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
 	DID2,	32,	// 0x4b - Device ID 2
diff --git a/src/southbridge/intel/i82801gx/nvs.h b/src/southbridge/intel/i82801gx/nvs.h
index a0f91cda68..6a178d2f3a 100644
--- a/src/southbridge/intel/i82801gx/nvs.h
+++ b/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	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
+	u16	rsvd14[3];
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];
diff --git a/src/southbridge/intel/i82801ix/acpi/globalnvs.asl b/src/southbridge/intel/i82801ix/acpi/globalnvs.asl
index a419fdb685..306260e58e 100644
--- a/src/southbridge/intel/i82801ix/acpi/globalnvs.asl
+++ b/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
diff --git a/src/southbridge/intel/i82801ix/nvs.h b/src/southbridge/intel/i82801ix/nvs.h
index cb4fb45519..815186591f 100644
--- a/src/southbridge/intel/i82801ix/nvs.h
+++ b/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	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
+	u16	rsvd14[3];
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];
diff --git a/src/southbridge/intel/i82801jx/acpi/globalnvs.asl b/src/southbridge/intel/i82801jx/acpi/globalnvs.asl
index 3c9dbc3f40..7d05ffbe98 100644
--- a/src/southbridge/intel/i82801jx/acpi/globalnvs.asl
+++ b/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
diff --git a/src/southbridge/intel/i82801jx/nvs.h b/src/southbridge/intel/i82801jx/nvs.h
index 26ecda33c8..e9e903711a 100644
--- a/src/southbridge/intel/i82801jx/nvs.h
+++ b/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	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
+	u16	rsvd14[3];
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];
diff --git a/src/southbridge/intel/ibexpeak/nvs.h b/src/southbridge/intel/ibexpeak/nvs.h
index a551fa473c..939b7e4cc8 100644
--- a/src/southbridge/intel/ibexpeak/nvs.h
+++ b/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	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
+	u16	rsvd14[3];
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	u8	rsvd5[0x9];
diff --git a/src/southbridge/intel/lynxpoint/acpi/globalnvs.asl b/src/southbridge/intel/lynxpoint/acpi/globalnvs.asl
index 149b75be6e..6dcec0dccc 100644
--- a/src/southbridge/intel/lynxpoint/acpi/globalnvs.asl
+++ b/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
diff --git a/src/southbridge/intel/lynxpoint/nvs.h b/src/southbridge/intel/lynxpoint/nvs.h
index 5222db2c45..3f2ce55766 100644
--- a/src/southbridge/intel/lynxpoint/nvs.h
+++ b/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	nste; /* 0x42 - next display state */
-	u16	sste; /* 0x44 - set display state */
+	u16	rsvd14[3];
 	u8	ndid; /* 0x46 - number of device ids */
 	u32	did[5]; /* 0x47 - 5b device id 1..5 */
 	/* TPM support */