hammer: Add board_get_entropy function (and test)

This function will be used to generate some entropy using the
Clock Recovery System.

BRANCH=none
BUG=b:38486828
TEST=make BOARD=hammer -j tests
     ./util/flash_ec --board=hammer --image=build/hammer/test-entropy.bin
     EC console: runtest
TEST=Test fails when no USB connection is active
TEST=Test passes when USB connection is active
TEST=Pasting the values into:
     tr ';' '\n' | awk 'BEGIN { e = 0; tot=16384.0 }
                  { p = $1/tot; if (p > 0) { e -= p*log(p)/log(2) } }
                  END { print e }'
     shows an entropy > 4 bits per sample.

Change-Id: I2363c7bce42c72c33ef0bf3f099d709ee9c13d13
Reviewed-on: https://chromium-review.googlesource.com/518608
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/test/entropy.tasklist b/test/entropy.tasklist
new file mode 100644
index 0000000000..e76178ba0a
--- /dev/null
+++ b/test/entropy.tasklist
@@ -0,0 +1,17 @@
+/* Copyright 2017 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.
+ */
+
+/**
+ * List of enabled tasks in the priority order
+ *
+ * The first one has the lowest priority.
+ *
+ * For each task, use the macro TASK_TEST(n, r, d, s) where :
+ * 'n' in the name of the task
+ * 'r' in the main routine of the task
+ * 'd' in an opaque parameter passed to the routine at startup
+ * 's' is the stack size in bytes; must be a multiple of 8
+ */
+#define CONFIG_TEST_TASK_LIST