Due to a HW issue, in some scenarios the LAST bit might remain set. This will cause an unexpected NACK after reading 16 bytes on the next read. Example: if user tries to read from a missing device, get a NACK, then if the next command is a long read ( > 16 bytes), the master will stop reading after 16 bytes. To solve this, if a command fails, check if LAST bit is still set. If it does, reset the module. Fixes: 56a1485b102e (i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver) Signed-off-by: Tali Perry <tali.perry1@xxxxxxxxx> --- drivers/i2c/busses/i2c-npcm7xx.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c index dfcf04e1967f..2ad166355ec9 100644 --- a/drivers/i2c/busses/i2c-npcm7xx.c +++ b/drivers/i2c/busses/i2c-npcm7xx.c @@ -2163,6 +2163,15 @@ static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, if (bus->cmd_err == -EAGAIN) ret = i2c_recover_bus(adap); + /* + * After any type of error, check if LAST bit is still set, + * due to a HW issue. + * It cannot be cleared without resetting the module. + */ + if (bus->cmd_err && + (NPCM_I2CRXF_CTL_LAST_PEC & ioread8(bus->reg + NPCM_I2CRXF_CTL))) + npcm_i2c_reset(bus); + #if IS_ENABLED(CONFIG_I2C_SLAVE) /* reenable slave if it was enabled */ if (bus->slave) base-commit: 856deb866d16e29bd65952e0289066f6078af773 -- 2.22.0
