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https://github.com/AsahiLinux/u-boot
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i2c: mvtwsi: Eliminate twsi_control_flags
In a system where the initial u-boot location is genuinely NOR flash (as opposed to RAM or a cache-line setup by a pre-bootloader) writes to the data section are problematic. At best these writes have no effect, at worst they put the flash memory into a status mode which changes the executable code underneath us. Pass around a stack variable from the top of the twsi i2c driver to avoid writing to global data. Signed-off-by: Chris Packham <judge.packham@gmail.com>
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3a3705280d
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1 changed files with 29 additions and 33 deletions
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@ -184,27 +184,18 @@ static int twsi_wait(struct i2c_adapter *adap, int expected_status)
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MVTWSI_ERROR_TIMEOUT, control, status, expected_status);
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MVTWSI_ERROR_TIMEOUT, control, status, expected_status);
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}
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}
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/*
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* These flags are ORed to any write to the control register
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* They allow global setting of TWSIEN and ACK.
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* By default none are set.
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* twsi_start() sets TWSIEN (in case the controller was disabled)
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* twsi_recv() sets ACK or resets it depending on expected status.
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*/
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static u8 twsi_control_flags = MVTWSI_CONTROL_TWSIEN;
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/*
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/*
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* Assert the START condition, either in a single I2C transaction
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* Assert the START condition, either in a single I2C transaction
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* or inside back-to-back ones (repeated starts).
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* or inside back-to-back ones (repeated starts).
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*/
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*/
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static int twsi_start(struct i2c_adapter *adap, int expected_status)
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static int twsi_start(struct i2c_adapter *adap, int expected_status, u8 *flags)
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{
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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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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/* globally set TWSIEN in case it was not */
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twsi_control_flags |= MVTWSI_CONTROL_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(twsi_control_flags | MVTWSI_CONTROL_START |
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writel(*flags | MVTWSI_CONTROL_START |
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MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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/* wait for controller to process START */
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/* wait for controller to process START */
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return twsi_wait(adap, expected_status);
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return twsi_wait(adap, expected_status);
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@ -213,14 +204,15 @@ static int twsi_start(struct i2c_adapter *adap, int expected_status)
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/*
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/*
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* Send a byte (i2c address or data).
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* Send a byte (i2c address or data).
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*/
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*/
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static int twsi_send(struct i2c_adapter *adap, u8 byte, int expected_status)
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static int twsi_send(struct i2c_adapter *adap, u8 byte, int expected_status,
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u8 *flags)
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{
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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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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/* put byte in data register for sending */
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writel(byte, &twsi->data);
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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'll cause sending */
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writel(twsi_control_flags | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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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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return twsi_wait(adap, expected_status);
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}
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}
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@ -229,18 +221,18 @@ static int twsi_send(struct i2c_adapter *adap, u8 byte, int expected_status)
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* Receive a byte.
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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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* Global mvtwsi_control_flags variable says if we should ack or nak.
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*/
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*/
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static int twsi_recv(struct i2c_adapter *adap, u8 *byte)
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static int twsi_recv(struct i2c_adapter *adap, u8 *byte, u8 *flags)
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{
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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int expected_status, status;
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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 global control flags */
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if (twsi_control_flags & MVTWSI_CONTROL_ACK)
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if (*flags & MVTWSI_CONTROL_ACK)
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expected_status = MVTWSI_STATUS_DATA_R_ACK;
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expected_status = MVTWSI_STATUS_DATA_R_ACK;
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else
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else
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expected_status = MVTWSI_STATUS_DATA_R_NAK;
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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(twsi_control_flags | MVTWSI_CONTROL_CLEAR_IFLG, &twsi->control);
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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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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 expected byte then store it */
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@ -296,8 +288,7 @@ static unsigned int twsi_calc_freq(const int n, const int m)
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static void twsi_reset(struct i2c_adapter *adap)
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static void twsi_reset(struct i2c_adapter *adap)
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{
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{
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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struct mvtwsi_registers *twsi = twsi_get_base(adap);
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/* ensure controller will be enabled by any twsi*() function */
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twsi_control_flags = MVTWSI_CONTROL_TWSIEN;
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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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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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@ -353,7 +344,7 @@ static void twsi_i2c_init(struct i2c_adapter *adap, int speed, int slaveadd)
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* Expected address status will derive from direction bit (bit 0) in addr.
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* Expected address status will derive from direction bit (bit 0) in addr.
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*/
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*/
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static int i2c_begin(struct i2c_adapter *adap, int expected_start_status,
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static int i2c_begin(struct i2c_adapter *adap, int expected_start_status,
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u8 addr)
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u8 addr, u8 *flags)
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{
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{
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int status, expected_addr_status;
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int status, expected_addr_status;
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@ -363,10 +354,11 @@ static int i2c_begin(struct i2c_adapter *adap, int expected_start_status,
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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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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);
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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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if (status == 0)
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status = twsi_send(adap, addr, expected_addr_status);
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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 ok or status of first failure to caller */
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return status;
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return status;
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}
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}
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@ -378,13 +370,14 @@ static int i2c_begin(struct i2c_adapter *adap, int expected_start_status,
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static int twsi_i2c_probe(struct i2c_adapter *adap, uchar chip)
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static int twsi_i2c_probe(struct i2c_adapter *adap, uchar chip)
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{
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{
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u8 dummy_byte;
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u8 dummy_byte;
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u8 flags = 0;
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int status;
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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);
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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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if (status == 0)
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status = twsi_recv(adap, &dummy_byte);
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status = twsi_recv(adap, &dummy_byte, &flags);
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/* Stop transaction */
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/* Stop transaction */
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twsi_stop(adap, 0);
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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 status of first failure */
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@ -405,27 +398,28 @@ 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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int alen, uchar *data, int length)
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{
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{
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int status;
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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));
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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 addr bytes */
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while ((status == 0) && alen--)
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while ((status == 0) && alen--)
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status = twsi_send(adap, addr >> (8*alen),
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status = twsi_send(adap, addr >> (8*alen),
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MVTWSI_STATUS_DATA_W_ACK);
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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 eeprom data bytes */
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if (status == 0)
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if (status == 0)
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status = i2c_begin(adap, MVTWSI_STATUS_REPEATED_START,
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status = i2c_begin(adap, MVTWSI_STATUS_REPEATED_START,
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(chip << 1) | 1);
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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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if (length > 0)
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twsi_control_flags |= MVTWSI_CONTROL_ACK;
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flags |= MVTWSI_CONTROL_ACK;
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/* now receive actual bytes */
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/* now receive actual bytes */
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while ((status == 0) && length--) {
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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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/* reset NAK if we if no more to read now */
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if (length == 0)
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if (length == 0)
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twsi_control_flags &= ~MVTWSI_CONTROL_ACK;
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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++);
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status = twsi_recv(adap, data++, &flags);
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}
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}
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/* Stop transaction */
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/* Stop transaction */
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status = twsi_stop(adap, status);
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status = twsi_stop(adap, status);
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@ -441,16 +435,18 @@ static int twsi_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
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int alen, uchar *data, int length)
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int alen, uchar *data, int length)
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{
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{
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int status;
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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 the eeprom adress bytes then data bytes */
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status = i2c_begin(adap, MVTWSI_STATUS_START, (chip << 1));
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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 addr bytes */
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while ((status == 0) && alen--)
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while ((status == 0) && alen--)
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status = twsi_send(adap, addr >> (8*alen),
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status = twsi_send(adap, addr >> (8*alen),
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MVTWSI_STATUS_DATA_W_ACK);
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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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while ((status == 0) && (length-- > 0))
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status = twsi_send(adap, *(data++), MVTWSI_STATUS_DATA_W_ACK);
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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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/* Stop transaction */
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status = twsi_stop(adap, status);
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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 status of first failure */
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