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i2c: npcm7xx: Clear LAST bit after a failed transaction.

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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: 56a1485b10 (i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver)
Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
This commit is contained in:
Tali Perry 2020-09-20 23:48:09 +03:00 committed by Wolfram Sang
parent a2bd970aa6
commit 8947efc077
1 changed files with 9 additions and 0 deletions
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9
drivers/i2c/busses/i2c-npcm7xx.c
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@ -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)