diff options
Diffstat (limited to 'drivers/i2c')
| -rw-r--r-- | drivers/i2c/mvtwsi.c | 129 |
1 files changed, 62 insertions, 67 deletions
diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c index 93bb88b06f..7b2c611228 100644 --- a/drivers/i2c/mvtwsi.c +++ b/drivers/i2c/mvtwsi.c @@ -14,8 +14,8 @@ #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) @@ -51,8 +51,8 @@ struct mvtwsi_registers { 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]; @@ -81,8 +81,8 @@ enum mvtwsi_ctrl_register_fields { }; /* - * 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 @@ -194,8 +194,8 @@ inline uint mvtwsi_error(uint ec, uint lc, uint ls, uint es) } /* - * 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) { @@ -214,7 +214,7 @@ 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, @@ -229,12 +229,12 @@ static int twsi_start(struct i2c_adapter *adap, int expected_status, u8 *flags) { 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); } @@ -246,42 +246,40 @@ static int twsi_send(struct i2c_adapter *adap, u8 byte, int 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) { @@ -289,15 +287,15 @@ 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) @@ -326,26 +324,26 @@ static void twsi_reset(struct i2c_adapter *adap) { 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); @@ -364,20 +362,19 @@ static void twsi_i2c_init(struct i2c_adapter *adap, int speed, int slaveadd) { 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, @@ -385,23 +382,23 @@ 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) @@ -410,26 +407,24 @@ 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) @@ -437,35 +432,34 @@ static int twsi_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr, 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, @@ -474,19 +468,20 @@ 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; } |