[linux-yocto] [kernel v5.2/standard/xlnx-soc][PATCH 1/2] i2c: cadence: do not clear bus_hold_flag in mrecv

[Quanyang Wang]

Hi,

On 10/14/19 2:07 PM, Michal Simek wrote:
> On 13. 10. 19 15:33, quanyang.wang at windriver.com wrote:
>> From: Quanyang Wang <quanyang.wang at windriver.com>
>>
>> When using i2c_smbus_read_byte_data to read one byte from a
>> slave device, because of the commit d358def70688
>> ("i2c: cadence: Fix the hold bit setting"), the transaction becomes:
>>
>> S Addr Wr [A] Comm [A] P S Addr Rd [A] [Data] NA P
>>                         ^
>>                  CR_HOLD bit as 0
>>
>> This will result that the read operation fails and will read "0xff" from
>> the slave device. In the SMBus protocol stipulates that it must follow that
>> command with a repeated START condition as below:
>>
>> S Addr Wr [A] Comm [A] Sr Addr Rd [A] [Data] NA P
>>
>> So keep CR_HOLD bit to be 1 to make sure that the read operation begins
>> with a Sr (repeated START) but not a STOP followed by START.
>>
>> Signed-off-by: Quanyang Wang <quanyang.wang at windriver.com>
>> ---
>>   drivers/i2c/busses/i2c-cadence.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
>> index 6b011931e090..d9493914be15 100644
>> --- a/drivers/i2c/busses/i2c-cadence.c
>> +++ b/drivers/i2c/busses/i2c-cadence.c
>> @@ -626,8 +626,6 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
>>   	 */
>>   	if ((id->recv_count > CDNS_I2C_FIFO_DEPTH)  || id->bus_hold_flag)
>>   		ctrl_reg |= CDNS_I2C_CR_HOLD;
>> -	else
>> -		ctrl_reg = ctrl_reg & ~CDNS_I2C_CR_HOLD;
>>   
>>   	cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);
>>   
>>
> Shubhrajyoti: Can you please comment?
Any comment?
>
> M