Messages in this thread | | | Date | Thu, 25 May 2023 16:30:26 +0700 | Subject | Re: [PATCH v1] i2c: designware: Handle invalid SMBus block data response length | From | Tam Chi Nguyen <> |
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Hi Jarkko
On 5/24/2023 19:33, Jarkko Nikula wrote: > Hi > > On 5/23/23 11:21, Tam Nguyen wrote: >> In I2C_FUNC_SMBUS_BLOCK_DATA case, the I2C Designware driver does not >> handle correctly when it receives the length of SMBus block data >> response from SMBus slave device, which is outside the range 1-32 bytes. >> Consequently, the I2C Designware bus is stuck and cannot recover. >> Because if IC_EMPTYFIFO_HOLD_MASTER_EN is set, which cannot be detected >> from the registers, the controller can be disabled if the STOP bit is >> set. >> But it is only set after receiving block data response length. >> >> Hence, to prevent the bus from stuck condition, after receiving the >> invalid block data response length, the driver will read another byte >> with STOP bit set. >> >> Cc: stable@vger.kernel.org >> Signed-off-by: Tam Nguyen <tamnguyenchi@os.amperecomputing.com> >> --- >> drivers/i2c/busses/i2c-designware-master.c | 15 +++++++++++++-- >> 1 file changed, 13 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-designware-master.c >> b/drivers/i2c/busses/i2c-designware-master.c >> index 55ea91a63382..94dadd785ed0 100644 >> --- a/drivers/i2c/busses/i2c-designware-master.c >> +++ b/drivers/i2c/busses/i2c-designware-master.c >> @@ -527,8 +527,19 @@ i2c_dw_read(struct dw_i2c_dev *dev) >> regmap_read(dev->map, DW_IC_DATA_CMD, &tmp); >> /* Ensure length byte is a valid value */ >> - if (flags & I2C_M_RECV_LEN && >> - (tmp & DW_IC_DATA_CMD_DAT) <= I2C_SMBUS_BLOCK_MAX && >> tmp > 0) { >> + if (flags & I2C_M_RECV_LEN) { >> + /* >> + * if IC_EMPTYFIFO_HOLD_MASTER_EN is set, which >> cannot be >> + * detected from the registers, the controller can be >> + * disabled if the STOP bit is set. But it is only set >> + * after receiving block data response length in >> + * I2C_FUNC_SMBUS_BLOCK_DATA case. That needs to read >> + * another byte with STOP bit set when the block data >> + * response length is invalid to complete the >> transaction. >> + */ >> + if ((tmp & DW_IC_DATA_CMD_DAT) > I2C_SMBUS_BLOCK_MAX >> || tmp == 0) >> + tmp = 1; >> + >> len = i2c_dw_recv_len(dev, tmp); >> } >> *buf++ = tmp; > > Looks otherwise good to me but I'm wondering the "tmp == 0" test can > it have the bit 11 set (on a HW where it's supported) and should it be > covered with DW_IC_DATA_CMD_DAT mask too? Please see commit > f53f15ba5a85 ("i2c: designware: Get right data length").
You're right. We should use the DW_IC_DATA_CMD_DAT mask to get the data part if HW supports reading bit 11 from IC_DATA_CMD. I will update it in v2.
Best regards, Tam Nguyen
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