UefiPayloadPkg: Add library for logging to EC

Make use of the SMFI command interface to forward logs from edk2 to
System76 EC.

Signed-off-by: Jeremy Soller <jeremy@system76.com>
Signed-off-by: Tim Crawford <tcrawford@system76.com>

UefiPayloadPkg/Library/System76EcLib/System76EcLib.c

@@ -0,0 +1,144 @@
+/** @file
+  System76 EC logging
+
+  Copyright (c) 2020 System76, Inc.
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/IoLib.h>
+
+// From coreboot/src/drivers/system76_ec/system76_ec.c {
+#define SYSTEM76_EC_BASE 0x0E00
+
+static inline UINT8 system76_ec_read(UINT8 addr) {
+    return IoRead8(SYSTEM76_EC_BASE + (UINT16)addr);
+}
+
+static inline void system76_ec_write(UINT8 addr, UINT8 data) {
+    IoWrite8(SYSTEM76_EC_BASE + (UINT16)addr, data);
+}
+
+void system76_ec_init(void) {
+    // Clear entire command region
+    for (int i = 0; i < 256; i++) {
+        system76_ec_write((UINT8)i, 0);
+    }
+}
+
+void system76_ec_flush(void) {
+    // Send command
+    system76_ec_write(0, 4);
+
+    // Wait for command completion
+    while (system76_ec_read(0) != 0) {}
+
+    // Clear length
+    system76_ec_write(3, 0);
+}
+
+void system76_ec_print(UINT8 byte) {
+    // Read length
+    UINT8 len = system76_ec_read(3);
+    // Write data at offset
+    system76_ec_write(len + 4, byte);
+    // Update length
+    system76_ec_write(3, len + 1);
+
+    // If we hit the end of the buffer, or were given a newline, flush
+    if (byte == '\n' || len >= 128) {
+        system76_ec_flush();
+    }
+}
+// } From coreboot/src/drivers/system76_ec/system76_ec.c
+
+// Implement SerialPortLib {
+#include <Library/SerialPortLib.h>
+
+RETURN_STATUS
+EFIAPI
+SerialPortInitialize (
+  VOID
+  )
+{
+    system76_ec_init();
+    return RETURN_SUCCESS;
+}
+
+UINTN
+EFIAPI
+SerialPortWrite (
+  IN UINT8     *Buffer,
+  IN UINTN     NumberOfBytes
+  )
+{
+    if (Buffer == NULL) {
+        return 0;
+    }
+
+    if (NumberOfBytes == 0) {
+        system76_ec_flush();
+        return 0;
+    }
+
+    for(UINTN i = 0; i < NumberOfBytes; i++) {
+        system76_ec_print(Buffer[i]);
+    }
+
+    return NumberOfBytes;
+}
+
+BOOLEAN
+EFIAPI
+SerialPortPoll (
+  VOID
+  )
+{
+    return FALSE;
+}
+
+RETURN_STATUS
+EFIAPI
+SerialPortGetControl (
+  OUT UINT32 *Control
+  )
+{
+    return RETURN_UNSUPPORTED;
+}
+
+RETURN_STATUS
+EFIAPI
+SerialPortSetControl (
+  IN UINT32 Control
+  )
+{
+    return RETURN_UNSUPPORTED;
+}
+
+RETURN_STATUS
+EFIAPI
+SerialPortSetAttributes (
+  IN OUT UINT64             *BaudRate,
+  IN OUT UINT32             *ReceiveFifoDepth,
+  IN OUT UINT32             *Timeout,
+  IN OUT EFI_PARITY_TYPE    *Parity,
+  IN OUT UINT8              *DataBits,
+  IN OUT EFI_STOP_BITS_TYPE *StopBits
+  )
+{
+    return RETURN_UNSUPPORTED;
+}
+// } Implement SerialPortLib
+
+// Implement PlatformHookLib {
+#include <Library/PlatformHookLib.h>
+
+RETURN_STATUS
+EFIAPI
+PlatformHookSerialPortInitialize (
+  VOID
+  )
+{
+    return RETURN_SUCCESS;
+}
+// } Implement PlatformHookLib