[PATCH v4 4/6] Platform/RaspberryPi4: Create ACPI fan object

["Jeremy Linton" <jeremy.linton@arm.com>]

Now that we have a thermal zone we can add active cooling
by specifying active cooling points (_ACx) which can
be tied to fan objects that turn fans on/off using GPIO
pins.

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Pete Batard <pete@akeo.ie>
Cc: Andrei Warkentin <awarkentin@vmware.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Pete Batard <@pbatard>
---
 Platform/RaspberryPi/AcpiTables/AcpiTables.inf  |  1 +
 Platform/RaspberryPi/AcpiTables/SsdtThermal.asl | 76 +++++++++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 Platform/RaspberryPi/AcpiTables/SsdtThermal.asl

diff --git a/Platform/RaspberryPi/AcpiTables/AcpiTables.inf b/Platform/RaspberryPi/AcpiTables/AcpiTables.inf
index 28d2afe197..c40c32e16f 100644
--- a/Platform/RaspberryPi/AcpiTables/AcpiTables.inf
+++ b/Platform/RaspberryPi/AcpiTables/AcpiTables.inf
@@ -33,6 +33,7 @@
   Csrt.aslc
   Spcr.aslc
   Pptt.aslc
+  SsdtThermal.asl
 
 [Packages]
   ArmPkg/ArmPkg.dec
diff --git a/Platform/RaspberryPi/AcpiTables/SsdtThermal.asl b/Platform/RaspberryPi/AcpiTables/SsdtThermal.asl
new file mode 100644
index 0000000000..ee028173e1
--- /dev/null
+++ b/Platform/RaspberryPi/AcpiTables/SsdtThermal.asl
@@ -0,0 +1,76 @@
+/** @file
+ *
+ *  Secondary System Description Table (SSDT) for active (fan) cooling
+ *
+ *  Copyright (c) 2020, Arm Ltd. All rights reserved.
+ *
+ *  SPDX-License-Identifier: BSD-2-Clause-Patent
+ *
+ **/
+
+#include <IndustryStandard/Bcm2711.h>
+#include <IndustryStandard/Bcm2836.h>
+#include <IndustryStandard/Bcm2836Gpio.h>
+
+#include <IndustryStandard/Acpi.h>
+
+DefinitionBlock (__FILE__, "SSDT", 5, "RPIFDN", "RPITHFAN", 2)
+{
+  External (\_SB_.EC00, DeviceObj)
+  External (\_SB_.EC00.TZ00, DeviceObj)
+
+  Scope (\_SB_.EC00)
+  {
+    // Define a NameOp we will modify during InstallTable
+    Name (GIOP, 0x2) //08 47 49 4f 50 0a 02 (value must be >1)
+    // Describe a fan
+    PowerResource (PFAN, 0, 0) {
+      OperationRegion (GPIO, SystemMemory, GPIO_BASE_ADDRESS, 0x1000)
+      Field (GPIO, DWordAcc, NoLock, Preserve) {
+        Offset (0x1C),
+        GPS0, 32,
+        GPS1, 32,
+        RES1, 32,
+        GPC0, 32,
+        GPC1, 32,
+        RES2, 32,
+        GPL1, 32,
+        GPL2, 32
+      }
+      // We are hitting a GPIO pin to on/off a fan.
+      // This assumes that UEFI has programmed the
+      // direction as OUT. Given the current limitations
+      // on the GPIO pins, its recommended to use
+      // the GPIO to switch a larger voltage/current
+      // for the fan rather than driving it directly.
+      Method (_STA) {
+        if (GPL1 & (1 << GIOP)) {
+          Return (1)                 // present and enabled
+        }
+        Return (0)
+      }
+      Method (_ON)  {                // turn fan on
+        Store (1 << GIOP, GPS0)
+      }
+      Method (_OFF) {                // turn fan off
+        Store (1 << GIOP, GPC0)
+      }
+    }
+    Device (FAN0) {
+      // Note, not currently an ACPIv4 fan
+      // the latter adds speed control/detection
+      // but in the case of linux needs FIF, FPS, FSL, and FST
+      Name (_HID, EISAID ("PNP0C0B"))
+      Name (_PR0, Package () { PFAN })
+    }
+  }
+
+  // merge in an active cooling point.
+  Scope (\_SB_.EC00.TZ00)
+  {
+    Method (_AC0) { Return (3332) }        // (60C) active cooling trip point,
+                                           // if this is lower than PSV then we
+                                           // prefer active cooling
+    Name (_AL0, Package () { \_SB_.EC00.FAN0 }) // the fan used for AC0 above
+  }
+}
-- 
2.13.7