Samus: Handle fan startup in the EC, not the fan controller

The fans on samus have a recommended minimum duty cycle of 20%
while running, but 30% in order to start. We've been using the
EC's built-in fan controller for the start requirement, but it
has a minimum fast-start duty cycle of 50%. It turns out that
that speed is noticeably noisy.

This change handles the startup with logic in the EC instead, so
that the fan only tries to spin at 30% initially (or if it drops
too much below the minimum turning speed).

BUG=chrome-os-partner:33429
BRANCH=ToT,samus
TEST=make buildall -j

Boot the system, let it idle with the browser windows closed, the
browse a bit, then idle. Listen for changes to the fans.

Before, I could hear the fans kick in and out as the AP load
changed. Now it's much quieter.

Change-Id: Id35215520c064eb6843686ec8bb5f3618dac6cf6
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/227658
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 108 insertions, 0 deletions

diff --git a/test/fan.c b/test/fan.c
new file mode 100644
index 0000000000..9a0fa0d225
--- /dev/null
+++ b/test/fan.c
@@ -0,0 +1,108 @@
+/* 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.
+ *
+ * Test thermal engine.
+ */
+
+#include "common.h"
+#include "console.h"
+#include "fan.h"
+#include "hooks.h"
+#include "host_command.h"
+#include "printf.h"
+#include "temp_sensor.h"
+#include "test_util.h"
+#include "thermal.h"
+#include "timer.h"
+#include "util.h"
+
+
+/*****************************************************************************/
+/* Tests */
+
+static int test_fan(void)
+{
+	/* "actual" fan speed from board/host/fan.c */
+	extern int mock_rpm;
+
+	sleep(2);
+
+	/* With nothing else to do, fans default to full-on */
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_max);
+
+	/*
+	 * fan_set_percent_needed() is normally called once a second by the
+	 * thermal task, but we're not using a thermal test in this test so
+	 * we can dink around with the fans without having to wait. The host
+	 * implementation just sets mock_rpm to whatever it's asked for.
+	 */
+
+	/* Off */
+	fan_set_percent_needed(0, 0);
+	TEST_ASSERT(fan_get_rpm_actual(0) == 0);
+	fan_set_percent_needed(0, 0);
+	TEST_ASSERT(fan_get_rpm_actual(0) == 0);
+
+	/* On, but just barely */
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_start);
+	/* fan is above min speed now, so should be set to min */
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_min);
+
+	/* Full speed */
+	fan_set_percent_needed(0, 100);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_max);
+	fan_set_percent_needed(0, 100);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_max);
+
+	/* Slow again */
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_min);
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_min);
+
+	/* Off */
+	fan_set_percent_needed(0, 0);
+	TEST_ASSERT(fan_get_rpm_actual(0) == 0);
+	fan_set_percent_needed(0, 0);
+	TEST_ASSERT(fan_get_rpm_actual(0) == 0);
+
+	/* On, but just barely */
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_start);
+	/* Force the mock_rpm to be slow, to simulate dragging */
+	mock_rpm = fans[0].rpm_min - 105;
+	/* It should keep trying for the start speed */
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_start);
+	/* But we have to keep forcing the mock_rpm back down */
+	mock_rpm = fans[0].rpm_min - 105;
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_start);
+	/* Now let it turn just under rpm_min. Should be okay there. */
+	mock_rpm = fans[0].rpm_min - 10;
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_min);
+	/* Let it go a little faster, still okay */
+	mock_rpm = fans[0].rpm_min + 10;
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_min);
+	/* But if it drops too low, it should go back to the start speed */
+	mock_rpm = fans[0].rpm_min - 105;
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_start);
+	/* And then relax */
+	fan_set_percent_needed(0, 1);
+	TEST_ASSERT(fan_get_rpm_actual(0) == fans[0].rpm_min);
+
+	return EC_SUCCESS;
+}
+
+void run_test(void)
+{
+	RUN_TEST(test_fan);
+
+	test_print_result();
+}