#include <asm/io.h>
/*
- * include a file that will provide CONFIG_I2C_MVTWSI_BASE*
- * and possibly other settings
+ * Include a file that will provide CONFIG_I2C_MVTWSI_BASE*, and possibly other
+ * settings
*/
#if defined(CONFIG_ORION5X)
u32 data;
u32 control;
union {
- u32 status; /* when reading */
- u32 baudrate; /* when writing */
+ u32 status; /* When reading */
+ u32 baudrate; /* When writing */
};
u32 xtnd_slave_addr;
u32 reserved[2];
};
/*
- * On sun6i and newer IFLG is a write-clear bit which is cleared by writing 1,
- * on other platforms it is a normal r/w bit which is cleared by writing 0.
+ * On sun6i and newer, IFLG is a write-clear bit, which is cleared by writing 1;
+ * on other platforms, it is a normal r/w bit, which is cleared by writing 0.
*/
#ifdef CONFIG_SUNXI_GEN_SUN6I
}
/*
- * Wait for IFLG to raise, or return 'timeout'; then if status is as expected,
- * return 0 (ok) or return 'wrong status'.
+ * Wait for IFLG to raise, or return 'timeout.' Then, if the status is as
+ * expected, return 0 (ok) or 'wrong status' otherwise.
*/
static int twsi_wait(struct i2c_adapter *adap, int expected_status)
{
MVTWSI_ERROR_WRONG_STATUS,
control, status, expected_status);
}
- udelay(10); /* one clock cycle at 100 kHz */
+ udelay(10); /* One clock cycle at 100 kHz */
} while (timeout--);
status = readl(&twsi->status);
return mvtwsi_error(MVTWSI_ERROR_TIMEOUT, control, status,
{
struct mvtwsi_registers *twsi = twsi_get_base(adap);
- /* globally set TWSIEN in case it was not */
+ /* Set TWSIEN */
*flags |= MVTWSI_CONTROL_TWSIEN;
- /* assert START */
+ /* Assert START */
writel(*flags | MVTWSI_CONTROL_START |
- MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
- /* wait for controller to process START */
+ MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
+ /* Wait for controller to process START */
return twsi_wait(adap, expected_status);
}
{
struct mvtwsi_registers *twsi = twsi_get_base(adap);
- /* put byte in data register for sending */
+ /* Write byte to data register for sending */
writel(byte, &twsi->data);
- /* clear any pending interrupt -- that'll cause sending */
+ /* Clear any pending interrupt -- that will cause sending */
writel(*flags | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
- /* wait for controller to receive byte and check ACK */
+ /* Wait for controller to receive byte, and check ACK */
return twsi_wait(adap, expected_status);
}
/*
* Receive a byte.
- * Global mvtwsi_control_flags variable says if we should ack or nak.
*/
static int twsi_recv(struct i2c_adapter *adap, u8 *byte, u8 *flags)
{
struct mvtwsi_registers *twsi = twsi_get_base(adap);
int expected_status, status;
- /* compute expected status based on ACK bit in global control flags */
+ /* Compute expected status based on ACK bit in passed control flags */
if (*flags & MVTWSI_CONTROL_ACK)
expected_status = MVTWSI_STATUS_DATA_R_ACK;
else
expected_status = MVTWSI_STATUS_DATA_R_NAK;
- /* acknowledge *previous state* and launch receive */
+ /* Acknowledge *previous state*, and launch receive */
writel(*flags | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
- /* wait for controller to receive byte and assert ACK or NAK */
+ /* Wait for controller to receive byte, and assert ACK or NAK */
status = twsi_wait(adap, expected_status);
- /* if we did receive expected byte then store it */
+ /* If we did receive the expected byte, store it */
if (status == 0)
*byte = readl(&twsi->data);
- /* return status */
return status;
}
/*
* Assert the STOP condition.
- * This is also used to force the bus back in idle (SDA=SCL=1).
+ * This is also used to force the bus back to idle (SDA = SCL = 1).
*/
static int twsi_stop(struct i2c_adapter *adap, int status)
{
int control, stop_status;
int timeout = 1000;
- /* assert STOP */
+ /* Assert STOP */
control = MVTWSI_CONTROL_TWSIEN | MVTWSI_CONTROL_STOP;
writel(control | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
- /* wait for IDLE; IFLG won't rise so twsi_wait() is no use. */
+ /* Wait for IDLE; IFLG won't rise, so we can't use twsi_wait() */
do {
stop_status = readl(&twsi->status);
if (stop_status == MVTWSI_STATUS_IDLE)
break;
- udelay(10); /* one clock cycle at 100 kHz */
+ udelay(10); /* One clock cycle at 100 kHz */
} while (timeout--);
control = readl(&twsi->control);
if (stop_status != MVTWSI_STATUS_IDLE)
{
struct mvtwsi_registers *twsi = twsi_get_base(adap);
- /* reset controller */
+ /* Reset controller */
writel(0, &twsi->soft_reset);
- /* wait 2 ms -- this is what the Marvell LSP does */
+ /* Wait 2 ms -- this is what the Marvell LSP does */
udelay(20000);
}
/*
- * I2C init called by cmd_i2c when doing 'i2c reset'.
- * Sets baud to the highest possible value not exceeding requested one.
+ * Sets baud to the highest possible value not exceeding the requested one.
*/
static unsigned int twsi_i2c_set_bus_speed(struct i2c_adapter *adap,
unsigned int requested_speed)
{
struct mvtwsi_registers *twsi = twsi_get_base(adap);
unsigned int tmp_speed, highest_speed, n, m;
- unsigned int baud = 0x44; /* baudrate at controller reset */
+ unsigned int baud = 0x44; /* Baud rate after controller reset */
- /* use actual speed to collect progressively higher values */
highest_speed = 0;
- /* compute m, n setting for highest speed not above requested speed */
+ /* Successively try m, n combinations, and use the combination
+ * resulting in the largest speed that's not above the requested
+ * speed */
for (n = 0; n < 8; n++) {
for (m = 0; m < 16; m++) {
tmp_speed = twsi_calc_freq(n, m);
{
struct mvtwsi_registers *twsi = twsi_get_base(adap);
- /* reset controller */
+ /* Reset controller */
twsi_reset(adap);
- /* set speed */
+ /* Set speed */
twsi_i2c_set_bus_speed(adap, speed);
- /* set slave address even though we don't use it */
+ /* Set slave address; even though we don't use it */
writel(slaveadd, &twsi->slave_address);
writel(0, &twsi->xtnd_slave_addr);
- /* assert STOP but don't care for the result */
+ /* Assert STOP, but don't care for the result */
(void) twsi_stop(adap, 0);
}
/*
* Begin I2C transaction with expected start status, at given address.
- * Common to i2c_probe, i2c_read and i2c_write.
* Expected address status will derive from direction bit (bit 0) in addr.
*/
static int i2c_begin(struct i2c_adapter *adap, int expected_start_status,
{
int status, expected_addr_status;
- /* compute expected address status from direction bit in addr */
- if (addr & 1) /* reading */
+ /* Compute the expected address status from the direction bit in
+ * the address byte */
+ if (addr & 1) /* Reading */
expected_addr_status = MVTWSI_STATUS_ADDR_R_ACK;
- else /* writing */
+ else /* Writing */
expected_addr_status = MVTWSI_STATUS_ADDR_W_ACK;
- /* assert START */
+ /* Assert START */
status = twsi_start(adap, expected_start_status, flags);
- /* send out the address if the start went well */
+ /* Send out the address if the start went well */
if (status == 0)
status = twsi_send(adap, addr, expected_addr_status,
flags);
- /* return ok or status of first failure to caller */
+ /* Return 0, or the status of the first failure */
return status;
}
/*
- * I2C probe called by cmd_i2c when doing 'i2c probe'.
* Begin read, nak data byte, end.
*/
static int twsi_i2c_probe(struct i2c_adapter *adap, uchar chip)
u8 flags = 0;
int status;
- /* begin i2c read */
+ /* Begin i2c read */
status = i2c_begin(adap, MVTWSI_STATUS_START, (chip << 1) | 1, &flags);
- /* dummy read was accepted: receive byte but NAK it. */
+ /* Dummy read was accepted: receive byte, but NAK it. */
if (status == 0)
status = twsi_recv(adap, &dummy_byte, &flags);
/* Stop transaction */
twsi_stop(adap, 0);
- /* return 0 or status of first failure */
+ /* Return 0, or the status of the first failure */
return status;
}
/*
- * I2C read called by cmd_i2c when doing 'i2c read' and by cmd_eeprom.c
* Begin write, send address byte(s), begin read, receive data bytes, end.
*
- * NOTE: some EEPROMS want a stop right before the second start, while
- * some will choke if it is there. Deciding which we should do is eeprom
- * stuff, not i2c, but at the moment the APIs won't let us put it in
- * cmd_eeprom, so we have to choose here, and for the moment that'll be
- * a repeated start without a preceding stop.
+ * NOTE: Some devices want a stop right before the second start, while some
+ * will choke if it is there. Since deciding this is not yet supported in
+ * higher level APIs, we need to make a decision here, and for the moment that
+ * will be a repeated start without a preceding stop.
*/
static int twsi_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
int alen, uchar *data, int length)
int status;
u8 flags = 0;
- /* begin i2c write to send the address bytes */
+ /* Begin i2c write to send the address bytes */
status = i2c_begin(adap, MVTWSI_STATUS_START, (chip << 1), &flags);
- /* send addr bytes */
+ /* Send address bytes */
while ((status == 0) && alen--)
status = twsi_send(adap, addr >> (8*alen),
MVTWSI_STATUS_DATA_W_ACK, &flags);
- /* begin i2c read to receive eeprom data bytes */
+ /* Begin i2c read to receive data bytes */
if (status == 0)
status = i2c_begin(adap, MVTWSI_STATUS_REPEATED_START,
(chip << 1) | 1, &flags);
- /* prepare ACK if at least one byte must be received */
+ /* Prepare ACK if at least one byte must be received */
if (length > 0)
flags |= MVTWSI_CONTROL_ACK;
- /* now receive actual bytes */
+ /* Receive actual data bytes */
while ((status == 0) && length--) {
- /* reset NAK if we if no more to read now */
+ /* Set NAK if we if we have nothing more to read */
if (length == 0)
flags &= ~MVTWSI_CONTROL_ACK;
- /* read current byte */
+ /* Read current byte */
status = twsi_recv(adap, data++, &flags);
}
/* Stop transaction */
status = twsi_stop(adap, status);
- /* return 0 or status of first failure */
+ /* Return 0, or the status of the first failure */
return status;
}
/*
- * I2C write called by cmd_i2c when doing 'i2c write' and by cmd_eeprom.c
* Begin write, send address byte(s), send data bytes, end.
*/
static int twsi_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
int status;
u8 flags = 0;
- /* begin i2c write to send the eeprom adress bytes then data bytes */
+ /* Begin i2c write to send first the address bytes, then the
+ * data bytes */
status = i2c_begin(adap, MVTWSI_STATUS_START, (chip << 1), &flags);
- /* send addr bytes */
+ /* Send address bytes */
while ((status == 0) && alen--)
status = twsi_send(adap, addr >> (8*alen),
MVTWSI_STATUS_DATA_W_ACK, &flags);
- /* send data bytes */
+ /* Send data bytes */
while ((status == 0) && (length-- > 0))
status = twsi_send(adap, *(data++), MVTWSI_STATUS_DATA_W_ACK,
&flags);
/* Stop transaction */
status = twsi_stop(adap, status);
- /* return 0 or status of first failure */
+ /* Return 0, or the status of the first failure */
return status;
}
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