summaryrefslogtreecommitdiffstats
path: root/src/drivers/bitbash
diff options
context:
space:
mode:
authorMichael Brown2006-06-11 02:57:00 +0200
committerMichael Brown2006-06-11 02:57:00 +0200
commit3ed40686c9cc0d05e5925890d157aeed7871fa70 (patch)
tree1d49679070715848ce3b10c5e97ebe8fd7e195e3 /src/drivers/bitbash
parentWindows Server 2003 sulks if we feed it an empty region in base memory (diff)
downloadipxe-3ed40686c9cc0d05e5925890d157aeed7871fa70.tar.gz
ipxe-3ed40686c9cc0d05e5925890d157aeed7871fa70.tar.xz
ipxe-3ed40686c9cc0d05e5925890d157aeed7871fa70.zip
Added bit-bashing i2c interface code
Diffstat (limited to 'src/drivers/bitbash')
-rw-r--r--src/drivers/bitbash/i2c_bit.c313
1 files changed, 313 insertions, 0 deletions
diff --git a/src/drivers/bitbash/i2c_bit.c b/src/drivers/bitbash/i2c_bit.c
new file mode 100644
index 00000000..9524d631
--- /dev/null
+++ b/src/drivers/bitbash/i2c_bit.c
@@ -0,0 +1,313 @@
+/*
+ * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <errno.h>
+#include <assert.h>
+#include <gpxe/bitbash.h>
+#include <gpxe/i2c.h>
+
+/** @file
+ *
+ * I2C bit-bashing interface
+ *
+ * This implements a simple I2C master via a bit-bashing interface
+ * that provides two lines: SCL (clock) and SDA (data).
+ */
+
+/**
+ * Set state of I2C SCL line
+ *
+ * @v basher Bit-bashing interface
+ * @v state New state of SCL
+ */
+static inline __attribute__ (( always_inline )) void
+setscl ( struct bit_basher *basher, int state ) {
+ write_bit ( basher, I2C_BIT_SCL, state );
+}
+
+/**
+ * Set state of I2C SDA line
+ *
+ * @v basher Bit-bashing interface
+ * @v state New state of SDA
+ */
+static inline __attribute__ (( always_inline )) void
+setsda ( struct bit_basher *basher, int state ) {
+ write_bit ( basher, I2C_BIT_SDA, state );
+}
+
+/**
+ * Get state of I2C SDA line
+ *
+ * @v basher Bit-bashing interface
+ * @ret state State of SDA
+ */
+static inline __attribute__ (( always_inline )) int
+getsda ( struct bit_basher *basher ) {
+ return read_bit ( basher, I2C_BIT_SDA );
+}
+
+/**
+ * Send an I2C start condition
+ *
+ * @v basher Bit-bashing interface
+ */
+static void i2c_start ( struct bit_basher *basher ) {
+ setscl ( basher, 1 );
+ setsda ( basher, 0 );
+ setscl ( basher, 0 );
+ setsda ( basher, 1 );
+}
+
+/**
+ * Send an I2C data bit
+ *
+ * @v basher Bit-bashing interface
+ * @v bit Bit to send
+ */
+static void i2c_send_bit ( struct bit_basher *basher, int bit ) {
+ setsda ( basher, bit );
+ setscl ( basher, 1 );
+ setscl ( basher, 0 );
+ setsda ( basher, 1 );
+}
+
+/**
+ * Receive an I2C data bit
+ *
+ * @v basher Bit-bashing interface
+ * @ret bit Received bit
+ */
+static int i2c_recv_bit ( struct bit_basher *basher ) {
+ int bit;
+
+ setscl ( basher, 1 );
+ bit = getsda ( basher );
+ setscl ( basher, 0 );
+ return bit;
+}
+
+/**
+ * Send an I2C stop condition
+ *
+ * @v basher Bit-bashing interface
+ */
+static void i2c_stop ( struct bit_basher *basher ) {
+ setsda ( basher, 0 );
+ setscl ( basher, 1 );
+ setsda ( basher, 1 );
+}
+
+/**
+ * Send byte via I2C bus and check for acknowledgement
+ *
+ * @v basher Bit-bashing interface
+ * @v byte Byte to send
+ * @ret rc Return status code
+ *
+ * Sends a byte via the I2C bus and checks for an acknowledgement from
+ * the slave device.
+ */
+static int i2c_send_byte ( struct bit_basher *basher, uint8_t byte ) {
+ int i;
+
+ /* Send byte */
+ for ( i = 8 ; i ; i-- ) {
+ i2c_send_bit ( basher, byte & 0x80 );
+ byte <<= 1;
+ }
+
+ /* Check for acknowledgement from slave */
+ return ( i2c_recv_bit ( basher ) == 0 ? 0 : -EIO );
+}
+
+/**
+ * Receive byte via I2C bus
+ *
+ * @v basher Bit-bashing interface
+ * @ret byte Received byte
+ *
+ * Receives a byte via the I2C bus and sends NACK to the slave device.
+ */
+static uint8_t i2c_recv_byte ( struct bit_basher *basher ) {
+ uint8_t value = 0;
+ int i;
+
+ /* Receive byte */
+ for ( i = 8 ; i ; i-- ) {
+ value <<= 1;
+ value |= i2c_recv_bit ( basher );
+ }
+
+ /* Send NACK */
+ i2c_send_bit ( basher, 1 );
+
+ return value;
+}
+
+/**
+ * Select I2C device for reading or writing
+ *
+ * @v basher Bit-bashing interface
+ * @v i2cdev I2C device
+ * @v direction I2C_READ or I2C_WRITE
+ * @ret rc Return status code
+ */
+static int i2c_select ( struct bit_basher *basher, struct i2c_device *i2cdev,
+ unsigned int direction ) {
+ unsigned int address;
+ int rc;
+
+ i2c_start ( basher );
+
+ /* First byte of the address */
+ address = i2cdev->address;
+ if ( i2cdev->tenbit ) {
+ address |= I2C_TENBIT_ADDRESS;
+ address >>= 8;
+ }
+ if ( ( rc = i2c_send_byte ( basher,
+ ( ( address << 1 ) | direction ) ) ) != 0 )
+ return rc;
+
+ /* Second byte of the address (10-bit addresses only) */
+ if ( i2cdev->tenbit ) {
+ if ( ( rc = i2c_send_byte ( basher,
+ ( i2cdev->address & 0xff ) ) ) !=0)
+ return rc;
+ }
+
+ return 0;
+}
+
+/**
+ * Read data from I2C device via bit-bashing interface
+ *
+ * @v i2c I2C interface
+ * @v i2cdev I2C device
+ * @v offset Starting offset within the device
+ * @v data Data buffer
+ * @v len Length of data buffer
+ * @ret rc Return status code
+ *
+ * Note that attempting to read zero bytes of data is a valid way to
+ * check for I2C device presence.
+ */
+static int i2c_bit_read ( struct i2c_interface *i2c,
+ struct i2c_device *i2cdev, unsigned int offset,
+ uint8_t *data, unsigned int len ) {
+ struct i2c_bit_basher *i2cbit
+ = container_of ( i2c, struct i2c_bit_basher, i2c );
+ struct bit_basher *basher = &i2cbit->basher;
+ int rc = 0;
+
+ DBG ( "Reading from I2C device %x: ", i2cdev->address );
+
+ while ( 1 ) {
+
+ /* Select device for writing */
+ if ( ( rc = i2c_select ( basher, i2cdev, I2C_WRITE ) ) != 0 )
+ break;
+
+ /* Abort at end of data */
+ if ( ! ( len-- ) )
+ break;
+
+ /* Select offset */
+ if ( ( rc = i2c_send_byte ( basher, offset++ ) ) != 0 )
+ break;
+
+ /* Select device for reading */
+ if ( ( rc = i2c_select ( basher, i2cdev, I2C_READ ) ) != 0 )
+ break;
+
+ /* Read byte */
+ *data++ = i2c_recv_byte ( basher );
+ DBG ( "%02x ", *(data - 1) );
+ }
+
+ DBG ( "%s\n", ( rc ? "failed" : "" ) );
+ i2c_stop ( basher );
+ return rc;
+}
+
+/**
+ * Write data to I2C device via bit-bashing interface
+ *
+ * @v i2c I2C interface
+ * @v i2cdev I2C device
+ * @v offset Starting offset within the device
+ * @v data Data buffer
+ * @v len Length of data buffer
+ * @ret rc Return status code
+ *
+ * Note that attempting to write zero bytes of data is a valid way to
+ * check for I2C device presence.
+ */
+static int i2c_bit_write ( struct i2c_interface *i2c,
+ struct i2c_device *i2cdev, unsigned int offset,
+ const uint8_t *data, unsigned int len ) {
+ struct i2c_bit_basher *i2cbit
+ = container_of ( i2c, struct i2c_bit_basher, i2c );
+ struct bit_basher *basher = &i2cbit->basher;
+ int rc = 0;
+
+ DBG ( "Writing to I2C device %x: ", i2cdev->address );
+
+ while ( 1 ) {
+
+ /* Select device for writing */
+ if ( ( rc = i2c_select ( basher, i2cdev, I2C_WRITE ) ) != 0 )
+ break;
+
+ /* Abort at end of data */
+ if ( ! ( len-- ) )
+ break;
+
+ /* Select offset */
+ if ( ( rc = i2c_send_byte ( basher, offset++ ) ) != 0 )
+ break;
+
+ /* Write data to device */
+ DBG ( "%02x ", *data );
+ if ( ( rc = i2c_send_byte ( basher, *data++ ) ) != 0 )
+ break;
+ }
+
+ DBG ( "%s\n", ( rc ? "failed" : "" ) );
+ i2c_stop ( basher );
+ return rc;
+}
+
+/**
+ * Initialise I2C bit-bashing interface
+ *
+ * @v i2cbit I2C bit-bashing interface
+ */
+void init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit ) {
+ struct bit_basher *basher = &i2cbit->basher;
+
+ assert ( basher->read != NULL );
+ assert ( basher->write != NULL );
+ i2cbit->i2c.read = i2c_bit_read;
+ i2cbit->i2c.write = i2c_bit_write;
+ basher->udelay = I2C_UDELAY;
+ i2c_stop ( basher );
+}