common: remove CONFIG_SMBUS dead code

CONFIG_SMBUS is not used.  Cleaning up the code by
removing this.

Added a comment to document the removal and why.  This will
give a way to find the code if we ever needed to bring it back

BUG=chromium:982316
BRANCH=none
TEST=make buildall

Change-Id: I40703a95bc849538e1aee32f6f96beab811285bd
Signed-off-by: Denis Brockus <dbrockus@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1704279
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>

5 files changed, 16 insertions, 342 deletions

diff --git a/common/build.mk b/common/build.mk
index 425a5ba4fc..61f64fca35 100644
--- a/common/build.mk
+++ b/common/build.mk
@@ -113,7 +113,6 @@ common-$(CONFIG_RWSIG_TYPE_RWSIG)+=vboot/vb21_lib.o
 common-$(CONFIG_MATH_UTIL)+=math_util.o
 common-$(CONFIG_SHA1)+= sha1.o
 common-$(CONFIG_SHA256)+=sha256.o
-common-$(CONFIG_SMBUS)+= smbus.o
 common-$(CONFIG_SOFTWARE_CLZ)+=clz.o
 common-$(CONFIG_SOFTWARE_CTZ)+=ctz.o
 common-$(CONFIG_CMD_SPI_XFER)+=spi_commands.o
diff --git a/common/smbus.c b/common/smbus.c
deleted file mode 100644
index dfe0dcc964..0000000000
--- a/common/smbus.c
+++ /dev/null
@@ -1,162 +0,0 @@
-/* Copyright 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.
- *
- * smbus cross-platform code for Chrome EC
- *  ref: http://smbus.org/specs/smbus20.pdf
- */
-
-#include "common.h"
-#include "console.h"
-#include "util.h"
-#include "i2c.h"
-#include "smbus.h"
-#include "crc8.h"
-
-#define CPRINTF(format, args...) cprintf(CC_I2C, format, ## args)
-
-/* Write 2 bytes using smbus word access protocol */
-int smbus_write_word(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint16_t d16)
-{
-	uint8_t buf[5];
-
-	/* Command sequence for CRC calculation */
-	buf[0] = slave_addr;
-	buf[1] = smbus_cmd;
-	buf[2] = d16 & 0xff;
-	buf[3] = (d16 >> 8) & 0xff;
-	buf[4] = crc8(buf, 4);
-	return i2c_xfer(i2c_port, slave_addr, buf + 1, 4, NULL, 0);
-}
-
-/* Write up to SMBUS_MAX_BLOCK_SIZE bytes using smbus block access protocol */
-int smbus_write_block(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint8_t *data, uint8_t len)
-{
-	uint8_t buf[3];
-	int rv;
-
-	/* Command sequence for CRC calculation */
-	buf[0] = slave_addr;
-	buf[1] = smbus_cmd;
-	buf[2] = len;
-
-	i2c_lock(i2c_port, 1);
-
-	/* Send command + length */
-	rv = i2c_xfer_unlocked(i2c_port, slave_addr,
-		      buf + 1, 2, NULL, 0, I2C_XFER_START);
-	if (rv != EC_SUCCESS)
-		goto smbus_write_block_done;
-
-	/* Send data */
-	rv = i2c_xfer_unlocked(i2c_port, slave_addr, data, len, NULL, 0, 0);
-	if (rv != EC_SUCCESS)
-		goto smbus_write_block_done;
-
-	/* Send CRC */
-	buf[0] = crc8(buf, 3);
-	buf[0] = crc8_arg(data, len, buf[0]);
-	rv = i2c_xfer_unlocked(i2c_port, slave_addr, buf, 1, NULL, 0,
-			I2C_XFER_STOP);
-
-smbus_write_block_done:
-	i2c_lock(i2c_port, 0);
-	return rv;
-}
-
-/* Read 2 bytes using smbus word access protocol */
-int smbus_read_word(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint16_t *p16)
-{
-	uint8_t buf[3];
-	int rv;
-	uint8_t crc;
-
-	/* Command sequence for CRC calculation */
-	buf[0] = slave_addr;
-	buf[1] = smbus_cmd;
-	buf[2] = slave_addr | 0x1;
-	crc = crc8(buf, 3);
-
-	/* Read data bytes + CRC byte */
-	rv = i2c_xfer(i2c_port, slave_addr, &smbus_cmd, 1, buf, 3);
-
-	/* Verify CRC */
-	if (crc8_arg(buf, 2, crc) != buf[2])
-		rv = EC_ERROR_CRC;
-
-	if (rv == EC_SUCCESS)
-		*p16 = (buf[1] << 8) | buf[0];
-	else
-		*p16 = 0;
-
-	return rv;
-}
-
-/* Read up to SMBUS_MAX_BLOCK_SIZE bytes using smbus block access protocol */
-int smbus_read_block(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint8_t *data, uint8_t *plen)
-{
-	int rv, read_len;
-	uint8_t buf[4];
-	uint8_t crc;
-	int do_crc = 1;
-
-	/* Command sequence for CRC calculation */
-	buf[0] = slave_addr;
-	buf[1] = smbus_cmd;
-	buf[2] = slave_addr | 0x1;
-
-	i2c_lock(i2c_port, 1);
-
-	/* First read size from slave */
-	rv = i2c_xfer_unlocked(i2c_port, slave_addr,
-		      &smbus_cmd, 1, buf + 3, 1, I2C_XFER_START);
-	if (rv != EC_SUCCESS)
-			goto smbus_read_block_done;
-	crc = crc8(buf, 4);
-
-	/*
-	 * If our input buffer isn't large enough to hold the entire input,
-	 * don't bother verifying crc since it may require reading numerous
-	 * data bytes that will be thrown away.
-	 */
-	read_len = MIN(buf[3], SMBUS_MAX_BLOCK_SIZE);
-	if (*plen < read_len) {
-		do_crc = 0;
-		read_len = *plen;
-	}
-
-	/* Now read back all bytes */
-	rv = i2c_xfer_unlocked(i2c_port, slave_addr,
-			NULL, 0, data, read_len, 0);
-	if (rv)
-		goto smbus_read_block_done;
-
-	/* Read CRC + verify */
-	rv = i2c_xfer_unlocked(i2c_port, slave_addr,
-		      NULL, 0, buf, 1, I2C_XFER_STOP);
-	if (do_crc && crc8_arg(data, read_len, crc) != buf[0])
-		rv = EC_ERROR_CRC;
-
-smbus_read_block_done:
-	if (rv != EC_SUCCESS)
-		memset(data, 0x0, *plen);
-	else
-		*plen = read_len;
-
-	i2c_lock(i2c_port, 0);
-	return rv;
-}
-
-int smbus_read_string(int i2c_port, uint8_t slave_addr, uint8_t smbus_cmd,
-			uint8_t *data, uint8_t len)
-{
-	int rv;
-	len -= 1;
-	rv = smbus_read_block(i2c_port, slave_addr, smbus_cmd, data, &len);
-	data[len] = '\0';
-	return rv;
-}
diff --git a/driver/battery/smart.c b/driver/battery/smart.c
index 4903b601fd..e42ebc726a 100644
--- a/driver/battery/smart.c
+++ b/driver/battery/smart.c
@@ -10,7 +10,6 @@
 #include "console.h"
 #include "host_command.h"
 #include "i2c.h"
-#include "smbus.h"
 #include "timer.h"
 #include "util.h"
 
@@ -31,17 +30,7 @@ test_mockable int sb_read(int cmd, int *param)
 	if (battery_is_cut_off())
 		return EC_RES_ACCESS_DENIED;
 #endif
-#ifdef CONFIG_SMBUS
-	{
-		int rv;
-		uint16_t d16 = 0;
-		rv = smbus_read_word(I2C_PORT_BATTERY, BATTERY_ADDR, cmd, &d16);
-		*param = d16;
-		return rv;
-	}
-#else
 	return i2c_read16(I2C_PORT_BATTERY, BATTERY_ADDR, cmd, param);
-#endif
 }
 
 test_mockable int sb_write(int cmd, int param)
@@ -53,11 +42,7 @@ test_mockable int sb_write(int cmd, int param)
 	if (battery_is_cut_off())
 		return EC_RES_ACCESS_DENIED;
 #endif
-#ifdef CONFIG_SMBUS
-	return smbus_write_word(I2C_PORT_BATTERY, BATTERY_ADDR, cmd, param);
-#else
 	return i2c_write16(I2C_PORT_BATTERY, BATTERY_ADDR, cmd, param);
-#endif
 }
 
 int sb_read_string(int offset, uint8_t *data, int len)
@@ -69,13 +54,8 @@ int sb_read_string(int offset, uint8_t *data, int len)
 	if (battery_is_cut_off())
 		return EC_RES_ACCESS_DENIED;
 #endif
-#ifdef CONFIG_SMBUS
-	return smbus_read_string(I2C_PORT_BATTERY, BATTERY_ADDR,
-				offset, data, len);
-#else
 	return i2c_read_string(I2C_PORT_BATTERY, BATTERY_ADDR,
 				offset, data, len);
-#endif
 }
 
 int sb_read_mfgacc(int cmd, int block, uint8_t *data, int len)
diff --git a/include/config.h b/include/config.h
index 546833b26f..3eb6d671d6 100644
--- a/include/config.h
+++ b/include/config.h
@@ -3054,7 +3054,22 @@
 #undef CONFIG_SOFTWARE_CTZ
 
 /* Support smbus interface */
-#undef CONFIG_SMBUS
+/*
+ * Deprecated in
+ * https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1704279
+ *
+ * It hasn't been used in over 2 years
+ * https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/452459/
+ * and was only used by one board (pyro).
+ *
+ * I2C and SMBus are compatible at the physical layer. The data transfer
+ * paradigm is different. Some of our batteries are using SMbus style
+ * transfers now, they are just using i2cxfer directly to accomplish it.
+ *
+ * I doubt the SMBus code will get revived, but we do have it in revision
+ * history if we ever need it.
+ */
+/* #undef CONFIG_SMBUS */
 
 /* Support SPI interfaces */
 #undef CONFIG_SPI
diff --git a/include/smbus.h b/include/smbus.h
deleted file mode 100644
index 41c0287dab..0000000000
--- a/include/smbus.h
+++ /dev/null
@@ -1,158 +0,0 @@
-/* Copyright 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.
- *
- * @file smbus.h
- * @brief smbus interface APIs
- * @see http://smbus.org/specs/smbus20.pdf
- */
-#ifndef __CROS_EC_SMBUS_H
-#define __CROS_EC_SMBUS_H
-
-/** Maximum transfer of a SMBUS block transfer */
-#define SMBUS_MAX_BLOCK_SIZE 32
-
-/**
- * smbus write word
- *   write 2 byte data + 1 byte pec
- */
-struct smbus_wr_word {
-	uint8_t slave_addr;/**< i2c_addr << 1 */
-	uint8_t smbus_cmd; /**< smbus cmd */
-	uint8_t data[3];   /**< smbus data */
-} __packed;
-
-/**
- * smbus write block data
- * smbus write 1 byte size + 32 byte data + 1 byte pec
- */
-struct smbus_wr_block {
-	uint8_t slave_addr;/**< i2c_addr << 1 */
-	uint8_t smbus_cmd; /**< smbus cmd */
-	uint8_t size;      /**< write size */
-	uint8_t data[SMBUS_MAX_BLOCK_SIZE+1];
-} __packed;
-
-/**
- * smbus read word
- * smbus read 2 byte + 1 pec
- */
-struct smbus_rd_word {
-	uint8_t slave_addr;   /**< i2c_addr << 1 */
-	uint8_t smbus_cmd;    /**< smbus cmd */
-	uint8_t slave_addr_rd;/**< (i2c_addr << 1) | 0x1 */
-	uint8_t data[3];      /**< smbus data */
-} __packed;
-
-/**
- * smbus read block data
- * smbus read 1 byte size + 32 byte data + 1 byte pec
- */
-struct smbus_rd_block {
-	uint8_t slave_addr;   /**< i2c_addr << 1 */
-	uint8_t smbus_cmd;    /**< smbus cmd */
-	uint8_t slave_addr_rd;/**< (i2c_addr << 1) | 0x1 */
-	uint8_t size;         /**< read block size */
-	uint8_t data[SMBUS_MAX_BLOCK_SIZE+1]; /**< smbus data */
-} __packed;
-
-/**
- * smbus_write_word
- * smbus write 2 bytes
- * @param i2c_port uint8_t, i2c port address
- * @param slave_addr uint8_t, i2c slave address:= (i2c_addr << 1)
- * @param smbus_cmd uint8_t, smbus command
- * @param d16 uint16_t, 2-bytes data
- * @return error_code
- *       EC_SUCCESS if success; none-zero if fail
- *       EC_ERROR_BUSY if interface is bussy
- *       none zero error code if fail
- */
-int smbus_write_word(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint16_t d16);
-
-/**
- * smbus_write_block
- * smbus write upto 32 bytes
- *   case 1:  n-1 byte data, 1 byte PEC
- *     [S][i2c Address][Wr=0][A][cmd][A] ...[Di][Ai]... [PEC][A][P]
- *
- *   case 2:  1 byte data-size, n -2 byte data, 1 byte PEC
- *     [S][i2c Address][Wr=0][A][cmd][A][size][A] ...[Di][Ai]... [PEC][A][P]
- *
- * @param i2c_port uint8_t, i2c port address
- * @param slave_addr uint8_t, i2c slave address:= (i2c_addr << 1)
- * @param smbus_cmd uint8_t, smbus command
- * @param data uint8_t *, n-bytes data
- * @param len uint8_t,  data length
- * @return error_code
- *       EC_SUCCESS if success; none-zero if fail
- *       EC_ERROR_BUSY if interface is bussy
- *       none zero error code if fail
- */
-int smbus_write_block(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint8_t *data, uint8_t len);
-
-/**
- * smbus_read_word
- * smbus read 2 bytes
- * @param i2c_port uint8_t, i2c port address
- * @param slave_addr uint8_t, i2c slave address:= (i2c_addr << 1)
- * @param smbus_cmd uint8_t, smbus command
- * @param p16 uint16_t *, a pointer to 2-bytes data
- * @return error_code
- *       EC_SUCCESS if success; none-zero if fail
- *       EC_ERROR_BUSY if interface is bussy
- *       none zero error code if fail
- */
-int smbus_read_word(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint16_t *p16);
-
-/**
- * smbus_read_block
- * smbus read upto 32 bytes
- * case 1:  n-1 byte data, 1 byte PEC
- *    [S][i2c addr][Wr=0][A][cmd][A]
- *    [S][i2c addr][Rd=1][A]...[Di][Ai]...[PEC][A][P]
- *
- * case 2:  1 byte data-size, n - 2 byte data, 1 byte PEC
- *    [S][i2c addr][Wr=0][A][cmd][A]
- *    [S][i2c addr][Rd=1][A][size][A]...[Di][Ai]...[PEC][A][P]
- *
- * @param i2c_port uint8_t, i2c port address
- * @param slave_addr uint8_t, i2c slave address:= (i2c_addr << 1)
- * @param smbus_cmd uint8_t, smbus command
- * @param data uint8_t *, n-bytes data
- * @param plen uint8_t *, a pointer data length
- * @return error_code
- *       EC_SUCCESS if success; none-zero if fail
- *       EC_ERROR_BUSY if interface is busy
- *       none zero error code if fail
- */
-int smbus_read_block(uint8_t i2c_port, uint8_t slave_addr,
-			uint8_t smbus_cmd, uint8_t *data, uint8_t *plen);
-
-/**
- * smbus_read_string
- * smbus read ascii string (upto 32-byte data + 1-byte NULL)
- * Read bytestream from <slaveaddr>:<smbus_cmd> with format:
- *     [length_N] [byte_0] [byte_1] ... [byte_N-1][byte_N='\0']
- *
- * <len>  : the max length of receiving buffer. to read N bytes
- *          ascii, len should be at least N+1 to include the
- *          terminating 0 (NULL).
- *
- * @param i2c_port uint8_t, i2c port address
- * @param slave_addr uint8_t, i2c slave address:= (i2c_addr << 1)
- * @param smbus_cmd uint8_t, smbus command
- * @param data uint8_t *, n-bytes data
- * @param len uint8_t,  data length
- * @return error_code
- *       EC_SUCCESS if success; none-zero if fail
- *       EC_ERROR_BUSY if interface is bussy
- *       none zero error code if fail
- */
-int smbus_read_string(int i2c_port, uint8_t slave_addr, uint8_t smbus_cmd,
-			uint8_t *data, uint8_t len);
-
-#endif /* __CROS_EC_SMBUS_H */