ec/system76/ec: Add manual fan control

system76/ec#512 added a manual fan control option.

In manual control mode, the system firmware or OS is responsible for
setting the fan target duty percent to manage thermals. Percent is used
rather than raw PWM value (as is returned in GFAN) as the EC may be
configured in such a way that the valid range is not 0-255.

Change-Id: Iba8cd5ac540f9fdc20473831787cafb6c1fd8129
Signed-off-by: Tim Crawford <tcrawford@system76.com>

Author: crawfxrd

src/ec/system76/ec/acpi/ec_ram.asl

@@ -42,6 +42,7 @@ Field (ERAM, ByteAcc, Lock, Preserve)
 	DUT2, 8,	// Fan 2 duty
 	RPM1, 16,	// Fan 1 RPM
 	RPM2, 16,	// Fan 2 RPM
+	FCTL, 8,	// Fan control mode
 	Offset (0xD9),
 	AIRP, 8,	// Airplane mode LED
 	WINF, 8,	// Enable ACPI brightness controls

src/ec/system76/ec/acpi/s76.asl

@@ -154,6 +154,36 @@ Device (S76D) {
 		Return ((Local1 << 8) | Local0)
 	}
 
+	// Set fan duty percent
+	// - Arg0: Fan select
+	// - Arg1: PWM duty percent
+	Method (SFDP, 2, Serialized) {
+		If (ToInteger (Arg1) > 100) {
+			Return (0xFF)
+		}
+
+		If (^^PCI0.LPCB.EC0.ECOK) {
+			// Fail here, but EC will also ignore writes if fan is
+			// set to automatic control.
+			If (^^PCI0.LPCB.EC0.FCTL == 0) {
+				Return (0xFF)
+			}
+
+			If (ToInteger (Arg0) == 0) {
+				^^PCI0.LPCB.EC0.DUT1 = Arg1
+				Return (0x00)
+			}
+#if CONFIG(EC_SYSTEM76_EC_FAN2)
+			If (ToInteger (Arg0) == 1) {
+				^^PCI0.LPCB.EC0.DUT2 = Arg1
+				Return (0x00)
+			}
+#endif
+		}
+
+		Return (0xFF)
+	}
+
 	// Temperature names
 	Method (NTMP, 0, Serialized) {
 		Return (Package() {
@@ -166,7 +196,7 @@ Device (S76D) {
 
 	// Get temperature
 	Method (GTMP, 1, Serialized) {
-		Local0 = 0;
+		Local0 = 0
 		If (^^PCI0.LPCB.EC0.ECOK) {
 			If (Arg0 == 0) {
 				Local0 = ^^PCI0.LPCB.EC0.TMP1
@@ -176,4 +206,32 @@ Device (S76D) {
 		}
 		Return (Local0)
 	}
+
+	// Get fan control mode
+	// - 0: EC automatic control
+	// - 1: EC manual control
+	Method (GFCM, 0, Serialized) {
+		Local0 = 0xFF
+		If (^^PCI0.LPCB.EC0.ECOK) {
+			Local0 = ^^PCI0.LPCB.EC0.FCTL
+		}
+		Return (Local0)
+	}
+
+	// Set fan control mode
+	// - 0: EC automatic control
+	// - 1: EC manual control
+	Method (SFCM, 1, Serialized) {
+		If (^^PCI0.LPCB.EC0.ECOK) {
+			Switch (ToInteger (Arg0)) {
+				Case (0x00) {
+					^^PCI0.LPCB.EC0.FCTL = Arg0
+				}
+
+				Case (0x01) {
+					^^PCI0.LPCB.EC0.FCTL = Arg0
+				}
+			}
+		}
+	}
 }