Cr50: Add stubs to support low-power idle

This just adds the framework to use for implementing sleep and
deep-sleep. This provides a custom idle task, and a new "idle"
console command to control what that task should do (nothing,
yet).

BUG=chrome-os-partner:49955
BRANCH=none
TEST=make buildall; test on Cr50

Other than the new idle command which does nothing, there is no
visible change. This is just a stub.

Change-Id: I8a9b82ca68dd6d1e3e7275f4f6753a23a7448f1d
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/336420
Reviewed-by: Randall Spangler <rspangler@chromium.org>

3 files changed, 81 insertions, 0 deletions

diff --git a/board/cr50/board.h b/board/cr50/board.h
index 90635323ae..d7cface787 100644
--- a/board/cr50/board.h
+++ b/board/cr50/board.h
@@ -21,6 +21,8 @@
 /* TODO(crosbug.com/p/44745): For debugging only */
 #define CONFIG_CMD_FLASH
 
+/* Go to sleep when nothing else is happening */
+#define CONFIG_LOW_POWER_IDLE
 
 /* USB configuration */
 #define CONFIG_USB
diff --git a/chip/g/build.mk b/chip/g/build.mk
index 0d8ae631b2..d6df5d228c 100644
--- a/chip/g/build.mk
+++ b/chip/g/build.mk
@@ -48,6 +48,8 @@ chip-$(CONFIG_USB_CONSOLE)+=usb_console.o
 chip-$(CONFIG_USB_HID)+=usb_hid.o
 chip-$(CONFIG_USB_BLOB)+=usb_blob.o
 
+chip-$(CONFIG_LOW_POWER_IDLE)+=idle.o
+
 chip-$(CONFIG_FLASH)+=flash.o
 dirs-y += chip/g/dcrypto
 
diff --git a/chip/g/idle.c b/chip/g/idle.c
new file mode 100644
index 0000000000..fc955e0b30
--- /dev/null
+++ b/chip/g/idle.c
@@ -0,0 +1,77 @@
+/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "common.h"
+#include "console.h"
+#include "util.h"
+
+/* This function is assumed to exist, but we don't use it */
+void clock_refresh_console_in_use(void)
+{
+}
+
+/* What to do when we're just waiting */
+static enum {
+	IDLE_WFI,				/* default */
+	IDLE_SLEEP,
+	IDLE_DEEP_SLEEP,
+	NUM_CHOICES
+} idle_action;
+
+static const char const *idle_name[] = {
+	"wfi",
+	"sleep",
+	"deep sleep",
+};
+BUILD_ASSERT(ARRAY_SIZE(idle_name) == NUM_CHOICES);
+
+static int command_idle(int argc, char **argv)
+{
+	int c, i;
+
+	if (argc > 1) {
+		c = tolower(argv[1][0]);
+		for (i = 0; i < ARRAY_SIZE(idle_name); i++)
+			if (idle_name[i][0] == c) {
+				idle_action = i;
+				break;
+			}
+	}
+
+	ccprintf("idle action: %s\n", idle_name[idle_action]);
+
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(idle, command_idle,
+			"[w|s|d]",
+			"Set or show the idle action: wfi, sleep, deep sleep",
+			NULL);
+
+/* Custom idle task, executed when no tasks are ready to be scheduled. */
+void __idle(void)
+{
+	while (1) {
+
+		/* Don't even bother unless we've enabled it */
+		if (idle_action == IDLE_WFI)
+			goto wfi;
+
+		/* TODO(wfrichar): sleep/deep-sleep stuff goes here... */
+
+wfi:
+		/* Wait for the next irq event. This stops the CPU clock and
+		 * may trigger sleep or deep sleep if enabled. */
+		asm("wfi");
+
+		/*
+		 * TODO: Normal sleep resumes by handling the interrupt, but we
+		 * need to clear PMU_LOW_POWER_DIS right away or we might sleep
+		 * again by accident. We can't do that here because we don't
+		 * get here until the next idle, so we'll have to do it in the
+		 * interrupt handler or when task switching. Deep sleep resumes
+		 * with a warm boot, which handles it differently.
+		 */
+	}
+}