bootstage: Require timer_get_boot_us() to be defined

At present we provide a default version of this function for use by
bootstage. However it uses the system timer and therefore likely requires
driver model. This makes it impossible to time driver-model init.

Drop the function and require boards to provide their own. Add a sandbox
version also. There is a default implememtation in lib/time.c for boards
which use CONFIG_SYS_TIMER_COUNTER.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/cpu.c

@@ -139,3 +139,14 @@ done:
 
 	return 0;
 }
+
+ulong timer_get_boot_us(void)
+{
+	static uint64_t base_count;
+	uint64_t count = os_get_nsec();
+
+	if (!base_count)
+		base_count = count;
+
+	return (count - base_count) / 1000;
+}

common/bootstage.c

@@ -8,7 +8,7 @@
 /*
  * This module records the progress of boot and arbitrary commands, and
  * permits accurate timestamping of each.
- *
+  *
  * TBD: Pass timings to kernel in the FDT
  */
 
@@ -292,23 +292,6 @@ void bootstage_report(void)
 	}
 }
 
-ulong __timer_get_boot_us(void)
-{
-	static ulong base_time;
-
-	/*
-	 * We can't implement this properly. Return 0 on the first call and
-	 * larger values after that.
-	 */
-	if (base_time)
-		return get_timer(base_time) * 1000;
-	base_time = get_timer(0);
-	return 0;
-}
-
-ulong timer_get_boot_us(void)
-	__attribute__((weak, alias("__timer_get_boot_us")));
-
 /**
  * Append data to a memory buffer
  *

include/bootstage.h

@@ -2,6 +2,7 @@
  * This file implements recording of each stage of the boot process. It is
  * intended to implement timing of each stage, reporting this information
  * to the user and passing it to the OS for logging / further analysis.
+ * Note that it requires timer_get_boot_us() to be defined by the board
  *
  * Copyright (c) 2011 The Chromium OS Authors.
  *
@@ -209,7 +210,7 @@ enum bootstage_id {
 /*
  * Return the time since boot in microseconds, This is needed for bootstage
  * and should be defined in CPU- or board-specific code. If undefined then
- * millisecond resolution will be used (the standard get_timer()).
+ * you will get a link error.
  */
 ulong timer_get_boot_us(void);