clock: define the function clock_enable_module to all EC chips

The API clock_enable_module(MODULE_FAST_CPU, x) allows common layer code
to set the CPU frequency to turbo or normal when it is needed.
However, not all of the EC chips support/implement the function. It
causes build error if this function is added to the common codes which
most of EC chips will use (EX: vboot_hash.) This CL fixes this issue by
defining the function as weak by default.

This CL also implements the clock_enable_module function for NPCX7 chip.

BRANCH=none
BUG=b:77608104
TEST=pass "make buildall"
TEST=on npcx7_evb/yorp, with follow-up CL, check that security
computation becomes faster and the clock goes back to normal frequency
after the computation finishes.

Change-Id: I731fb38f5fc1a4efa5fb331a59f8c3e2803ca30a
Signed-off-by: CHLin <CHLIN56@nuvoton.com>
Reviewed-on: https://chromium-review.googlesource.com/1475097
Commit-Ready: CH Lin <chlin56@nuvoton.com>
Tested-by: CH Lin <chlin56@nuvoton.com>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/common/system.c b/common/system.c
index 6cd5702c30..467218560a 100644
--- a/common/system.c
+++ b/common/system.c
@@ -1632,3 +1632,13 @@ int board_write_serial(const char *serialno)
 }
 #endif
 #endif  /* CONFIG_SERIALNO_LEN */
+
+
+__attribute__((weak))
+void clock_enable_module(enum module_id module, int enable)
+{
+	/*
+	 * Default weak implementation - for chips that don't support this
+	 * function.
+	 */
+}