soc/amd/*: Fix UART ACPI device status

Prior to commit d1c0f958d198 ("acpi: Call acpi_fill_ssdt() only for
enabled devices"), uart_inject_ssdt() was used to set the ACPI status
(_STA) for both enabled and disabled devices. The aforementioned commit
limited it to being called only on enabled devices, which left disabled
devices without any _STA method at all -- which the OS assumes means
that the device is present and enabled.

To fix this, create the _STA method in the UART asl code for each port,
and set the return value to a name variable (STAT) which defaults to
0 (not present/disabled). Then, have uart_inject_ssdt() set STAT to
present and enabled (0xF) for UARTs actually present on the board.

TEST=build/boot google/skyrim (frostflow), dump ACPI tables, and verify
that _STA returns 0xF only for UARTs enabled in devicetree.

Change-Id: Id89e74c3ea7f53280935898ee35311b7cf3b152a
Signed-off-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77092
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/soc/amd/cezanne/acpi/mmio.asl b/src/soc/amd/cezanne/acpi/mmio.asl
index e73c423600..722f32d573 100644
--- a/src/soc/amd/cezanne/acpi/mmio.asl
+++ b/src/soc/amd/cezanne/acpi/mmio.asl
@@ -87,6 +87,12 @@ Device (FUR0)
 		}
 	}
 
+	Name (STAT, 0x0)
+	Method (_STA, 0x0, NotSerialized)
+	{
+		Return (STAT)
+	}
+
 	AOAC_DEVICE(FCH_AOAC_DEV_UART0, 0)
 }
 
@@ -118,6 +124,12 @@ Device (FUR1) {
 		}
 	}
 
+	Name (STAT, 0x0)
+	Method (_STA, 0x0, NotSerialized)
+	{
+		Return (STAT)
+	}
+
 	AOAC_DEVICE(FCH_AOAC_DEV_UART1, 0)
 }