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i2c: mvtwsi: Improve and fix comments
This patch fixes only comments/documentation: Streamline capitalization and improve grammar/punctuation. Signed-off-by: Mario Six <mario.six@gdsys.cc> Reviewed-by: Stefan Roese <sr@denx.de>
This commit is contained in:
mario.six@gdsys.cc
Heiko Schocher
parent
dfc3958cd3
commit
49c801bf35
@ -14,8 +14,8 @@
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#include <asm/io.h>
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/*
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* include a file that will provide CONFIG_I2C_MVTWSI_BASE*
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* and possibly other settings
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* Include a file that will provide CONFIG_I2C_MVTWSI_BASE*, and possibly other
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* settings
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*/
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#if defined(CONFIG_ORION5X)
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@ -51,8 +51,8 @@ struct mvtwsi_registers {
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u32 data;
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u32 control;
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union {
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u32 status; /* when reading */
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u32 baudrate; /* when writing */
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u32 status; /* When reading */
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u32 baudrate; /* When writing */
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};
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u32 xtnd_slave_addr;
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u32 reserved[2];
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@ -81,8 +81,8 @@ enum mvtwsi_ctrl_register_fields {
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};
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/*
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* On sun6i and newer IFLG is a write-clear bit which is cleared by writing 1,
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* on other platforms it is a normal r/w bit which is cleared by writing 0.
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* On sun6i and newer, IFLG is a write-clear bit, which is cleared by writing 1;
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* on other platforms, it is a normal r/w bit, which is cleared by writing 0.
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*/
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#ifdef CONFIG_SUNXI_GEN_SUN6I
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@ -194,8 +194,8 @@ inline uint mvtwsi_error(uint ec, uint lc, uint ls, uint es)
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}
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/*
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* Wait for IFLG to raise, or return 'timeout'; then if status is as expected,
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* return 0 (ok) or return 'wrong status'.
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* Wait for IFLG to raise, or return 'timeout.' Then, if the status is as
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* expected, return 0 (ok) or 'wrong status' otherwise.
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*/
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static int twsi_wait(struct i2c_adapter *adap, int expected_status)
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{
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@ -214,7 +214,7 @@ static int twsi_wait(struct i2c_adapter *adap, int expected_status)
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MVTWSI_ERROR_WRONG_STATUS,
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control, status, expected_status);
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}
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udelay(10); /* one clock cycle at 100 kHz */
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udelay(10); /* One clock cycle at 100 kHz */
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} while (timeout--);
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status = readl(&twsi->status);
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return mvtwsi_error(MVTWSI_ERROR_TIMEOUT, control, status,
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@ -229,12 +229,12 @@ static int twsi_start(struct i2c_adapter *adap, int expected_status, u8 *flags)
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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/* globally set TWSIEN in case it was not */
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/* Set TWSIEN */
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*flags |= MVTWSI_CONTROL_TWSIEN;
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/* assert START */
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/* Assert START */
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writel(*flags | MVTWSI_CONTROL_START |
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MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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/* wait for controller to process START */
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MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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/* Wait for controller to process START */
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return twsi_wait(adap, expected_status);
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}
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@ -246,42 +246,40 @@ static int twsi_send(struct i2c_adapter *adap, u8 byte, int expected_status,
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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/* put byte in data register for sending */
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/* Write byte to data register for sending */
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writel(byte, &twsi->data);
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/* clear any pending interrupt -- that'll cause sending */
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/* Clear any pending interrupt -- that will cause sending */
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writel(*flags | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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/* wait for controller to receive byte and check ACK */
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/* Wait for controller to receive byte, and check ACK */
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return twsi_wait(adap, expected_status);
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}
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/*
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* Receive a byte.
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* Global mvtwsi_control_flags variable says if we should ack or nak.
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*/
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static int twsi_recv(struct i2c_adapter *adap, u8 *byte, u8 *flags)
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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int expected_status, status;
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/* compute expected status based on ACK bit in global control flags */
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/* Compute expected status based on ACK bit in passed control flags */
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if (*flags & MVTWSI_CONTROL_ACK)
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expected_status = MVTWSI_STATUS_DATA_R_ACK;
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else
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expected_status = MVTWSI_STATUS_DATA_R_NAK;
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/* acknowledge *previous state* and launch receive */
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/* Acknowledge *previous state*, and launch receive */
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writel(*flags | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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/* wait for controller to receive byte and assert ACK or NAK */
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/* Wait for controller to receive byte, and assert ACK or NAK */
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status = twsi_wait(adap, expected_status);
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/* if we did receive expected byte then store it */
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/* If we did receive the expected byte, store it */
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if (status == 0)
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*byte = readl(&twsi->data);
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/* return status */
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return status;
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}
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/*
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* Assert the STOP condition.
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* This is also used to force the bus back in idle (SDA=SCL=1).
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* This is also used to force the bus back to idle (SDA = SCL = 1).
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*/
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static int twsi_stop(struct i2c_adapter *adap, int status)
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{
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@ -289,15 +287,15 @@ static int twsi_stop(struct i2c_adapter *adap, int status)
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int control, stop_status;
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int timeout = 1000;
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/* assert STOP */
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/* Assert STOP */
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control = MVTWSI_CONTROL_TWSIEN | MVTWSI_CONTROL_STOP;
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writel(control | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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/* wait for IDLE; IFLG won't rise so twsi_wait() is no use. */
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/* Wait for IDLE; IFLG won't rise, so we can't use twsi_wait() */
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do {
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stop_status = readl(&twsi->status);
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if (stop_status == MVTWSI_STATUS_IDLE)
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break;
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udelay(10); /* one clock cycle at 100 kHz */
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udelay(10); /* One clock cycle at 100 kHz */
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} while (timeout--);
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control = readl(&twsi->control);
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if (stop_status != MVTWSI_STATUS_IDLE)
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@ -326,26 +324,26 @@ static void twsi_reset(struct i2c_adapter *adap)
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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/* reset controller */
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/* Reset controller */
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writel(0, &twsi->soft_reset);
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/* wait 2 ms -- this is what the Marvell LSP does */
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/* Wait 2 ms -- this is what the Marvell LSP does */
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udelay(20000);
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}
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/*
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* I2C init called by cmd_i2c when doing 'i2c reset'.
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* Sets baud to the highest possible value not exceeding requested one.
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* Sets baud to the highest possible value not exceeding the requested one.
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*/
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static unsigned int twsi_i2c_set_bus_speed(struct i2c_adapter *adap,
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unsigned int requested_speed)
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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unsigned int tmp_speed, highest_speed, n, m;
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unsigned int baud = 0x44; /* baudrate at controller reset */
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unsigned int baud = 0x44; /* Baud rate after controller reset */
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/* use actual speed to collect progressively higher values */
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highest_speed = 0;
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/* compute m, n setting for highest speed not above requested speed */
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/* Successively try m, n combinations, and use the combination
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* resulting in the largest speed that's not above the requested
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* speed */
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for (n = 0; n < 8; n++) {
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for (m = 0; m < 16; m++) {
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tmp_speed = twsi_calc_freq(n, m);
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@ -364,20 +362,19 @@ static void twsi_i2c_init(struct i2c_adapter *adap, int speed, int slaveadd)
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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/* reset controller */
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/* Reset controller */
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twsi_reset(adap);
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/* set speed */
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/* Set speed */
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twsi_i2c_set_bus_speed(adap, speed);
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/* set slave address even though we don't use it */
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/* Set slave address; even though we don't use it */
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writel(slaveadd, &twsi->slave_address);
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writel(0, &twsi->xtnd_slave_addr);
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/* assert STOP but don't care for the result */
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/* Assert STOP, but don't care for the result */
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(void) twsi_stop(adap, 0);
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}
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/*
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* Begin I2C transaction with expected start status, at given address.
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* Common to i2c_probe, i2c_read and i2c_write.
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* Expected address status will derive from direction bit (bit 0) in addr.
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*/
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static int i2c_begin(struct i2c_adapter *adap, int expected_start_status,
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@ -385,23 +382,23 @@ static int i2c_begin(struct i2c_adapter *adap, int expected_start_status,
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{
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int status, expected_addr_status;
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/* compute expected address status from direction bit in addr */
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if (addr & 1) /* reading */
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/* Compute the expected address status from the direction bit in
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* the address byte */
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if (addr & 1) /* Reading */
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expected_addr_status = MVTWSI_STATUS_ADDR_R_ACK;
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else /* writing */
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else /* Writing */
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expected_addr_status = MVTWSI_STATUS_ADDR_W_ACK;
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/* assert START */
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/* Assert START */
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status = twsi_start(adap, expected_start_status, flags);
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/* send out the address if the start went well */
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/* Send out the address if the start went well */
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if (status == 0)
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status = twsi_send(adap, addr, expected_addr_status,
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flags);
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/* return ok or status of first failure to caller */
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/* Return 0, or the status of the first failure */
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return status;
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}
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/*
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* I2C probe called by cmd_i2c when doing 'i2c probe'.
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* Begin read, nak data byte, end.
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*/
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static int twsi_i2c_probe(struct i2c_adapter *adap, uchar chip)
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@ -410,26 +407,24 @@ static int twsi_i2c_probe(struct i2c_adapter *adap, uchar chip)
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u8 flags = 0;
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int status;
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/* begin i2c read */
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/* Begin i2c read */
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status = i2c_begin(adap, MVTWSI_STATUS_START, (chip << 1) | 1, &flags);
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/* dummy read was accepted: receive byte but NAK it. */
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/* Dummy read was accepted: receive byte, but NAK it. */
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if (status == 0)
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status = twsi_recv(adap, &dummy_byte, &flags);
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/* Stop transaction */
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twsi_stop(adap, 0);
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/* return 0 or status of first failure */
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/* Return 0, or the status of the first failure */
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return status;
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}
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/*
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* I2C read called by cmd_i2c when doing 'i2c read' and by cmd_eeprom.c
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* Begin write, send address byte(s), begin read, receive data bytes, end.
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*
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* NOTE: some EEPROMS want a stop right before the second start, while
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* some will choke if it is there. Deciding which we should do is eeprom
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* stuff, not i2c, but at the moment the APIs won't let us put it in
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* cmd_eeprom, so we have to choose here, and for the moment that'll be
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* a repeated start without a preceding stop.
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* NOTE: Some devices want a stop right before the second start, while some
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* will choke if it is there. Since deciding this is not yet supported in
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* higher level APIs, we need to make a decision here, and for the moment that
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* will be a repeated start without a preceding stop.
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*/
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static int twsi_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
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int alen, uchar *data, int length)
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@ -437,35 +432,34 @@ static int twsi_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
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int status;
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u8 flags = 0;
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/* begin i2c write to send the address bytes */
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/* Begin i2c write to send the address bytes */
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status = i2c_begin(adap, MVTWSI_STATUS_START, (chip << 1), &flags);
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/* send addr bytes */
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/* Send address bytes */
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while ((status == 0) && alen--)
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status = twsi_send(adap, addr >> (8*alen),
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MVTWSI_STATUS_DATA_W_ACK, &flags);
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/* begin i2c read to receive eeprom data bytes */
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/* Begin i2c read to receive data bytes */
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if (status == 0)
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status = i2c_begin(adap, MVTWSI_STATUS_REPEATED_START,
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(chip << 1) | 1, &flags);
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/* prepare ACK if at least one byte must be received */
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/* Prepare ACK if at least one byte must be received */
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if (length > 0)
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flags |= MVTWSI_CONTROL_ACK;
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/* now receive actual bytes */
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/* Receive actual data bytes */
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while ((status == 0) && length--) {
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/* reset NAK if we if no more to read now */
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/* Set NAK if we if we have nothing more to read */
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if (length == 0)
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flags &= ~MVTWSI_CONTROL_ACK;
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/* read current byte */
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/* Read current byte */
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status = twsi_recv(adap, data++, &flags);
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}
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/* Stop transaction */
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status = twsi_stop(adap, status);
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/* return 0 or status of first failure */
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/* Return 0, or the status of the first failure */
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return status;
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}
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/*
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* I2C write called by cmd_i2c when doing 'i2c write' and by cmd_eeprom.c
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* Begin write, send address byte(s), send data bytes, end.
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*/
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static int twsi_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
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@ -474,19 +468,20 @@ static int twsi_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
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int status;
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u8 flags = 0;
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/* begin i2c write to send the eeprom adress bytes then data bytes */
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/* Begin i2c write to send first the address bytes, then the
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* data bytes */
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status = i2c_begin(adap, MVTWSI_STATUS_START, (chip << 1), &flags);
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/* send addr bytes */
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/* Send address bytes */
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while ((status == 0) && alen--)
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status = twsi_send(adap, addr >> (8*alen),
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MVTWSI_STATUS_DATA_W_ACK, &flags);
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/* send data bytes */
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/* Send data bytes */
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while ((status == 0) && (length-- > 0))
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status = twsi_send(adap, *(data++), MVTWSI_STATUS_DATA_W_ACK,
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&flags);
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/* Stop transaction */
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status = twsi_stop(adap, status);
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/* return 0 or status of first failure */
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/* Return 0, or the status of the first failure */
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return status;
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}
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