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, 2 insertions, 4 deletions

diff --git a/src/soc/amd/common/block/uart/uart.c b/src/soc/amd/common/block/uart/uart.c
index 96b9883b8c..ca678fd59b 100644
--- a/src/soc/amd/common/block/uart/uart.c
+++ b/src/soc/amd/common/block/uart/uart.c
@@ -67,13 +67,11 @@ static const char *uart_acpi_name(const struct device *dev)
 		return NULL;
 }
 
-/* This gets called for both enabled and disabled devices. */
+/* This gets called for enabled devices only. */
 static void uart_inject_ssdt(const struct device *dev)
 {
 	acpigen_write_scope(acpi_device_path(dev));
-
-	acpigen_write_STA(acpi_device_status(dev));
-
+	acpigen_write_store_int_to_namestr(acpi_device_status(dev), "STAT");
 	acpigen_pop_len(); /* Scope */
 }
 #endif