Re: [PATCH 1/4] i2c: rockchip: fix i2c stop condition

[Gerald Loacker <gerald.loacker@wolfvision.net>]

Am 08.09.2023 um 15:53 schrieb Sascha Hauer:
> On Fri, Sep 08, 2023 at 12:16:46PM +0200, Gerald Loacker wrote:
>> The i2c bus gets disabled without sending a stop condition. This violates
>> i2c timing on the clock line. Fix this and include all related functions
>> (rk_i2c_send_start_bit, rk_i2c_send_stop_bit, rk_i2c_disable) onto the same
>> level.
>>
>> Signed-off-by: Gerald Loacker <gerald.loacker@wolfvision.net>
>> ---
>>  drivers/i2c/busses/i2c-rockchip.c | 21 ++++++++-------------
>>  1 file changed, 8 insertions(+), 13 deletions(-)
>>
>> @@ -387,6 +376,11 @@ static int rockchip_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>>  		struct i2c_msg *msg = &msgs[i];
>>  
>>  		dev_dbg(dev, "i2c_xfer: chip=0x%x, len=0x%x\n", msg->addr, msg->len);
>> +
>> +		ret = rk_i2c_send_start_bit(i2c);
>> +		if (ret)
>> +			break;
>> +
>>  		if (msg->flags & I2C_M_RD) {
>>  			ret = rk_i2c_read(i2c, msg->addr, 0, 0, msg->buf,
>>  					  msg->len);
>> @@ -394,6 +388,9 @@ static int rockchip_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>>  			ret = rk_i2c_write(i2c, msg->addr, 0, 0, msg->buf,
>>  					   msg->len);
>>  		}
>> +
>> +		rk_i2c_send_stop_bit(i2c);
>> +
>>  		if (ret) {
>>  			dev_dbg(dev, "i2c_write: error sending: %pe\n",
>>  				ERR_PTR(ret));
>> @@ -402,9 +399,7 @@ static int rockchip_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
>>  		}
>>  	}
>>  
>> -	rk_i2c_send_stop_bit(i2c);
> 
> I believe this is wrong. A stop bit should only be sent after the last
> message, not after all messages.
> 

Your're right. This was just because the repeated start does not work
consitently in our case. I'll come up with another approach.

Gerald

> Sascha
>