| Message ID | 20171204081618.5922-1-wsa+renesas@sang-engineering.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | i2c: algo-bit: init the bus to a known state | expand |
On Mon, Dec 04, 2017 at 09:16:18AM +0100, Wolfram Sang wrote: > Ensure the bus is free when we register the adapter. Before the SCL/SDA > wires were in an unknown state. It used to work because sending a byte > has a retry mechanism which was triggered if the bus was initially in a > not-free state. But the graceful way to do it is to initialize > correctly, of course. > > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Applied to for-next, thanks!
diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index 1147bddb8b2c8a..3df0efd69ae336 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -649,6 +649,11 @@ static int __i2c_bit_add_bus(struct i2c_adapter *adap, if (bit_adap->getscl == NULL) adap->quirks = &i2c_bit_quirk_no_clk_stretch; + /* Bring bus to a known state. Looks like STOP if bus is not free yet */ + setscl(bit_adap, 1); + udelay(bit_adap->udelay); + setsda(bit_adap, 1); + ret = add_adapter(adap); if (ret < 0) return ret;
Ensure the bus is free when we register the adapter. Before the SCL/SDA wires were in an unknown state. It used to work because sending a byte has a retry mechanism which was triggered if the bus was initially in a not-free state. But the graceful way to do it is to initialize correctly, of course. Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> --- Found while working with the I2C GPIO fault injector. SCL was initially low before, so it only worked on the second try. drivers/i2c/algos/i2c-algo-bit.c | 5 +++++ 1 file changed, 5 insertions(+)