Hi, On Thu, Jun 20, 2019 at 07:25:25PM +0000, Boyang Yu wrote: > max6658 may report unrealistically high temperature during > the driver initialization, for which, its overtemp alarm pin > also gets asserted. For certain devices implementing overtemp > protection based on that pin, it may further trigger a reset to > the device. By reproducing the problem, the wrong reading is > found to be coincident with changing the conversion rate. > > To mitigate this issue, set the stop bit before changing the > conversion rate and unset it thereafter. After such change, the > wrong reading is not reproduced. As the issue is only found on > max6658, apply this change only to the max6657 kind. > > Signed-off-by: Boyang Yu <b...@arista.com> > --- > drivers/hwmon/lm90.c | 54 ++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 50 insertions(+), 4 deletions(-) [ ... ] > > /* > * Set conversion rate. > * client->update_lock must be held when calling this function (unless we are > @@ -587,7 +616,11 @@ static int lm90_set_convrate(struct i2c_client *client, > struct lm90_data *data, > if (interval >= update_interval * 3 / 4) > break; > > - err = i2c_smbus_write_byte_data(client, LM90_REG_W_CONVRATE, i); > + if (data->kind == max6657) > + err = max6657_write_convrate(client, i); > + else > + err = i2c_smbus_write_byte_data(client, LM90_REG_W_CONVRATE, i); > + Please name the new function lm90_write_convrate, call it unconditionally, and check if the chip is affected in the function. Also, please implement the check with a feature flag - it is quite unlikely that only max6658 is affected, and we'll want an easy method to add support for other chips.
Thanks, Guenter
