4.19-stable review patch. If anyone has any objections, please let me know.
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From: Alain Volmat alain.volmat@foss.st.com
commit c896ff2dd8f30a6b0a922c83a96f6d43f05f0e92 upstream.
In case of SMBUS byte read with PEC enabled, the whole transfer is split into two commands. A first write command, followed by a read command. The write command does not have any PEC byte and a PEC byte is appended at the end of the read command. (cf Read byte protocol with PEC in SMBUS specification)
Within the STM32 I2C controller, handling (either sending or receiving) of the PEC byte is done via the PECBYTE bit in register CR2.
Currently, the PECBYTE is set at the beginning of a transfer, which lead to sending a PEC byte at the end of the write command (hence losing the real last byte), and also does not check the PEC byte received during the read command.
This patch corrects the function stm32f7_i2c_smbus_xfer_msg in order to only set the PECBYTE during the read command.
Fixes: 9e48155f6bfe ("i2c: i2c-stm32f7: Add initial SMBus protocols support") Signed-off-by: Alain Volmat alain.volmat@foss.st.com Reviewed-by: Pierre-Yves MORDRET pierre-yves.mordret@foss.st.com Acked-by: Andi Shyti andi.shyti@kernel.org Signed-off-by: Wolfram Sang wsa@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/i2c/busses/i2c-stm32f7.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/drivers/i2c/busses/i2c-stm32f7.c +++ b/drivers/i2c/busses/i2c-stm32f7.c @@ -959,9 +959,10 @@ static int stm32f7_i2c_smbus_xfer_msg(st /* Configure PEC */ if ((flags & I2C_CLIENT_PEC) && f7_msg->size != I2C_SMBUS_QUICK) { cr1 |= STM32F7_I2C_CR1_PECEN; - cr2 |= STM32F7_I2C_CR2_PECBYTE; - if (!f7_msg->read_write) + if (!f7_msg->read_write) { + cr2 |= STM32F7_I2C_CR2_PECBYTE; f7_msg->count++; + } } else { cr1 &= ~STM32F7_I2C_CR1_PECEN; cr2 &= ~STM32F7_I2C_CR2_PECBYTE; @@ -1049,8 +1050,10 @@ static void stm32f7_i2c_smbus_rep_start( f7_msg->stop = true;
/* Add one byte for PEC if needed */ - if (cr1 & STM32F7_I2C_CR1_PECEN) + if (cr1 & STM32F7_I2C_CR1_PECEN) { + cr2 |= STM32F7_I2C_CR2_PECBYTE; f7_msg->count++; + }
/* Set number of bytes to be transferred */ cr2 &= ~(STM32F7_I2C_CR2_NBYTES_MASK);