On 3/9/21 3:35 PM, Chris Packham wrote: > > On 8/03/21 1:31 pm, Guenter Roeck wrote: >> On 3/7/21 2:52 PM, Chris Packham wrote: >>> Fundamentally I think this is a problem with the fact that the LM81 is >>> an SMBus device but the T2080 (and other Freescale SoCs) uses i2c and we >>> emulate SMBus. I suspect the errant readings are when we don't get round >>> to completing the read within the timeout specified by the SMBus >>> specification. Depending on when that happens we either fail the >>> transfer or interpret the result as all-1s. >> That is quite unlikely. Many sensor chips are SMBus chips connected to >> i2c busses. It is much more likely that there is a bug in the T2080 i2c driver, >> that the chip doesn't like the bulk read command issued through regmap, that >> the chip has problems with the i2c bus speed, or that the i2c bus is noisy. > I have noticed that with the switch to regmap we end up using plain i2c > instead of SMBUS. There appears to be no way of saying use SMBUS > semantics if the i2c adapter reports I2C_FUNC_I2C. > The driver only really supports I2C; SMBUS functions are emulated. I don't think that makes a real difference. Guenter
