soc/intel/skylake: Enable UART debug controller on S3 resume

1. Add a new variable to GNVS to store information during S3 suspend
whether UART debug port controller is enabled.

2. On resume, read stored GNVS variable to decide if UART debug port
controller needs to be initialized.

3. Provide helpers functions required by intel/common UART driver for
enabling controller on S3 resume.

BUG=b:64030366
TEST=Verified behavior with different combinations:
1. Serial console enabled in coreboot: No change in behavior.
2. Serial console enabled only in kernel: coreboot initializes debug
controller on S3 resume.
3. Serial console not enabled in coreboot and kernel: coreboot skips
initialization of debug controller on S3 resume.

Change-Id: Iad1cc974bc396ecd55b05ebb6591eec6cedfa16c
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/20886
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

5 files changed, 27 insertions, 7 deletions

diff --git a/src/soc/intel/skylake/Makefile.inc b/src/soc/intel/skylake/Makefile.inc
index 7f618d42be..baf6f01751 100644
--- a/src/soc/intel/skylake/Makefile.inc
+++ b/src/soc/intel/skylake/Makefile.inc
@@ -76,6 +76,7 @@ smm-y += pmutil.c
 smm-y += smihandler.c
 smm-$(CONFIG_SPI_FLASH_SMM) += spi.c
 smm-$(CONFIG_UART_DEBUG) += uart_debug.c
+smm-y += uart.c
 
 postcar-y += memmap.c
 postcar-$(CONFIG_UART_DEBUG) += uart_debug.c
diff --git a/src/soc/intel/skylake/acpi/globalnvs.asl b/src/soc/intel/skylake/acpi/globalnvs.asl
index d06269f2ae..8a7606c6ec 100644
--- a/src/soc/intel/skylake/acpi/globalnvs.asl
+++ b/src/soc/intel/skylake/acpi/globalnvs.asl
@@ -66,6 +66,7 @@ Field (GNVS, ByteAcc, NoLock, Preserve)
 	CID1,	16,	// 0x3d - Wifi Country Identifier
 	U2WE,	16,	// 0x3f - USB2 Wake Enable Bitmap
 	U3WE,	8,	// 0x41 - USB3 Wake Enable Bitmap
+	UIOR,	8,	// 0x42 - UART debug controller init on S3 resume
 
 	/* ChromeOS specific */
 	Offset (0x100),
diff --git a/src/soc/intel/skylake/include/soc/nvs.h b/src/soc/intel/skylake/include/soc/nvs.h
index 4ca3d227b0..8272336e87 100644
--- a/src/soc/intel/skylake/include/soc/nvs.h
+++ b/src/soc/intel/skylake/include/soc/nvs.h
@@ -57,7 +57,8 @@ typedef struct {
 	u16	cid1; /* 0x3d - Wifi Country Identifier */
 	u16	u2we; /* 0x3f - USB2 Wake Enable Bitmap */
 	u8	u3we; /* 0x41 - USB3 Wake Enable Bitmap */
-	u8	unused[190];
+	u8	uior; /* 0x42 - UART debug controller init on S3 resume */
+	u8	unused[189];
 
 	/* ChromeOS specific (0x100 - 0xfff) */
 	chromeos_acpi_t chromeos;
diff --git a/src/soc/intel/skylake/smihandler.c b/src/soc/intel/skylake/smihandler.c
index c4c4a7b975..d87994ea16 100644
--- a/src/soc/intel/skylake/smihandler.c
+++ b/src/soc/intel/skylake/smihandler.c
@@ -24,6 +24,7 @@
 #include <elog.h>
 #include <intelblocks/fast_spi.h>
 #include <intelblocks/pcr.h>
+#include <intelblocks/uart.h>
 #include <delay.h>
 #include <device/pci_def.h>
 #include <elog.h>
@@ -165,6 +166,8 @@ static void southbridge_smi_sleep(void)
 	case ACPI_S3:
 		printk(BIOS_DEBUG, "SMI#: Entering S3 (Suspend-To-RAM)\n");
 
+		gnvs->uior = uart_debug_controller_is_initialized();
+
 		/* Invalidate the cache before going to S3 */
 		wbinvd();
 		break;
diff --git a/src/soc/intel/skylake/uart.c b/src/soc/intel/skylake/uart.c
index 07326d5eb3..4e65859ea7 100644
--- a/src/soc/intel/skylake/uart.c
+++ b/src/soc/intel/skylake/uart.c
@@ -14,22 +14,20 @@
  * GNU General Public License for more details.
  */
 
+#include <cbmem.h>
 #include <device/pci.h>
 #include <intelblocks/uart.h>
 #include <soc/iomap.h>
+#include <soc/nvs.h>
 #include <soc/pci_devs.h>
 
-static int pch_uart_is_debug(struct device *dev)
-{
-	return dev->path.pci.devfn == PCH_DEVFN_UART2;
-}
-
+#if !ENV_SMM
 void pch_uart_read_resources(struct device *dev)
 {
 	pci_dev_read_resources(dev);
 
 	/* Set the configured UART base address for the debug port */
-	if (IS_ENABLED(CONFIG_UART_DEBUG) && pch_uart_is_debug(dev)) {
+	if (IS_ENABLED(CONFIG_UART_DEBUG) && uart_is_debug_controller(dev)) {
 		struct resource *res = find_resource(dev, PCI_BASE_ADDRESS_0);
 		/* Need to set the base and size for the resource allocator. */
 		res->base = UART_DEBUG_BASE_ADDRESS;
@@ -38,3 +36,19 @@ void pch_uart_read_resources(struct device *dev)
 			IORESOURCE_FIXED;
 	}
 }
+#endif
+
+bool pch_uart_init_debug_controller_on_resume(void)
+{
+	global_nvs_t *gnvs = cbmem_find(CBMEM_ID_ACPI_GNVS);
+
+	if (gnvs)
+		return !!gnvs->uior;
+
+	return false;
+}
+
+device_t pch_uart_get_debug_controller(void)
+{
+	return PCH_DEV_UART2;
+}