i2c: Support changing I2C bus speed at runtime

Add a i2c_set_freq function and let chip drivers add their underlying
implementation.

Also implemented on stm32f0.

BUG=b:143677811,b:78189419
TEST=1) make
     2) On kodama, call i2c_set_freq(1, 100) during init.
        verify the bus is configured to 100kbps in kodama rev 1
BRANCH=kukui

Change-Id: Iebb5baacf098b3e5649a4bd8ca14acf097d39693
Signed-off-by: Ting Shen <phoenixshen@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1969245
Reviewed-by: Matthew Blecker <matthewb@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>
Commit-Queue: Ting Shen <phoenixshen@chromium.org>
Tested-by: Ting Shen <phoenixshen@chromium.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/chip/host/i2c.c b/chip/host/i2c.c
index 5b863c1d41..f474c38ef1 100644
--- a/chip/host/i2c.c
+++ b/chip/host/i2c.c
@@ -7,6 +7,7 @@
 
 #include "hooks.h"
 #include "i2c.h"
+#include "i2c_private.h"
 #include "link_defs.h"
 #include "test_util.h"
 
@@ -95,6 +96,26 @@ int chip_i2c_xfer(const int port, const uint16_t slave_addr_flags,
 	return EC_ERROR_UNKNOWN;
 }
 
+int chip_i2c_set_freq(int port, enum i2c_freq freq)
+{
+	return EC_ERROR_UNIMPLEMENTED;
+}
+
+enum i2c_freq chip_i2c_get_freq(int port)
+{
+	switch (i2c_ports[port].kbps) {
+	case 1000:
+		return I2C_FREQ_1000KHZ;
+	case 400:
+		return I2C_FREQ_400KHZ;
+	case 100:
+		return I2C_FREQ_100KHZ;
+	}
+
+	/* fallback to 100k */
+	return I2C_FREQ_100KHZ;
+}
+
 int i2c_raw_get_scl(int port)
 {
 	return 1;