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Subject[PATCH v1] i2c: npcm7xx: Clear LAST bit after a failed transaction.
Date
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@gmail.com>
---
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

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