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>

2 files changed, 80 insertions, 21 deletions

diff --git a/include/i2c.h b/include/i2c.h
index 247306da7d..b9feac13d8 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -66,6 +66,9 @@
 /* The size of the header for a version 3 response packet sent over I2C. */
 #define I2C_RESPONSE_HEADER_SIZE 2
 
+/* This port allows changing speed at runtime */
+#define I2C_PORT_FLAG_DYNAMIC_SPEED	BIT(0)
+
 /*
  * Supported I2C CLK frequencies.
  * TODO(crbug.com/549286): Use this enum in i2c_port_t.
@@ -113,6 +116,7 @@ struct i2c_port_t {
 	int (*passthru_allowed)(const struct i2c_port_t *port,
 				uint16_t addr_flags);
 	const struct i2c_drv *drv;
+	uint16_t flags;       /* I2C_PORT_FLAG_* flags */
 };
 
 extern const struct i2c_port_t i2c_ports[];
@@ -196,27 +200,6 @@ int i2c_xfer_unlocked(const int port,
 #define I2C_LINE_IDLE (I2C_LINE_SCL_HIGH | I2C_LINE_SDA_HIGH)
 
 /**
- * Chip-level function to transmit one block of raw data, then receive one
- * block of raw data.
- *
- * This is a low-level chip-dependent function and should only be called by
- * i2c_xfer().
- *
- * @param port		Port to access
- * @param slave_addr	Slave device address
- * @param out		Data to send
- * @param out_size	Number of bytes to send
- * @param in		Destination buffer for received data
- * @param in_size	Number of bytes to receive
- * @param flags		Flags (see I2C_XFER_* above)
- * @return EC_SUCCESS, or non-zero if error.
- */
-int chip_i2c_xfer(const int port,
-		  const uint16_t slave_addr_flags,
-		  const uint8_t *out, int out_size,
-		  uint8_t *in, int in_size, int flags);
-
-/**
  * Return raw I/O line levels (I2C_LINE_*) for a port when port is in alternate
  * function mode.
  *
@@ -580,4 +563,24 @@ void i2c_end_xfer_notify(const int port,
 void i2c_trace_notify(int port, uint16_t slave_addr_flags,
 		      int direction, const uint8_t *data, size_t size);
 
+/**
+ * Set bus speed. Only support for ports with I2C_PORT_FLAG_DYNAMIC_SPEED
+ * flag.
+ *
+ * @param port:		Port to access
+ * @param freq:		Bus speed.
+ *
+ * @return EC_SUCCESS, or non-zero if error.
+ */
+int i2c_set_freq(int port, enum i2c_freq freq);
+
+/**
+ * Chip level function to get bus speed.
+ *
+ * @param port:		Port to access
+ *
+ * @return Bus speed
+ */
+enum i2c_freq i2c_get_freq(int port);
+
 #endif  /* __CROS_EC_I2C_H */
diff --git a/include/i2c_private.h b/include/i2c_private.h
new file mode 100644
index 0000000000..8a92884c16
--- /dev/null
+++ b/include/i2c_private.h
@@ -0,0 +1,56 @@
+/* Copyright 2020 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.
+ */
+
+/*
+ * Private chipset-specific implementations that only accessible by
+ * i2c_master.c. Don't include this directly unless you are implementing
+ * these functions.
+ */
+#ifndef __CROS_EC_I2C_PRIVATE_H
+#define __CROS_EC_I2C_PRIVATE_H
+
+#include "i2c.h"
+
+/**
+ * Chip-level function to transmit one block of raw data, then receive one
+ * block of raw data.
+ *
+ * This is a low-level chip-dependent function and should only be called by
+ * i2c_xfer().
+ *
+ * @param port		Port to access
+ * @param slave_addr	Slave device address
+ * @param out		Data to send
+ * @param out_size	Number of bytes to send
+ * @param in		Destination buffer for received data
+ * @param in_size	Number of bytes to receive
+ * @param flags		Flags (see I2C_XFER_* above)
+ * @return EC_SUCCESS, or non-zero if error.
+ */
+int chip_i2c_xfer(const int port,
+		  const uint16_t slave_addr_flags,
+		  const uint8_t *out, int out_size,
+		  uint8_t *in, int in_size, int flags);
+
+/**
+ * Chip level function to set bus speed.
+ *
+ * @param port:		Port to access
+ * @param kbps:		Bus speed in kbps.
+ *
+ * @return EC_SUCCESS, or non-zero if error.
+ */
+int chip_i2c_set_freq(int port, enum i2c_freq freq);
+
+/**
+ * Chip level function to get bus speed.
+ *
+ * @param port:		Port to access
+ *
+ * @return Bus speed
+ */
+enum i2c_freq chip_i2c_get_freq(int port);
+
+#endif /* __CROS_EC_I2C_PRIVATE_H */