On Wed, Oct 17, 2018 at 01:53:48PM -0700, Nicolin Chen wrote: > Hello Guenter, > > On Wed, Oct 17, 2018 at 09:55:43AM -0700, Guenter Roeck wrote: > > > @@ -676,6 +701,13 @@ static int __maybe_unused ina3221_resume(struct device *dev) > > > if (ret) > > > return ret; > > > > > > + /* Make sure data conversion is finished */ > > > + ret = ina3221_wait_for_data_if_active(ina); > > > > This is quite expensive and would delay resume (and enable, for that matter). > > A less expensive solution would be to save the enable time here and in > > ina3221_write_enable(). ina3221_wait_for_data_if_active() can then be called > > from read functions and would wait if not enough time has expired. > > > > if (time_before(...)) > > usleep_range(missing wait time, missing_wait_time * 2); > > > > or something like that. This could be done per channel or, to keep > > things simple, just using a single time for all channels. > > I was thinking something that'd fit one-shot mode too so decided > to add a polling. But you are right. It does make sense to skip > polling until an actual read happens, though it also feels a bit > reasonable to me that putting a polling to the enabling routine. > > The wait time would be sightly more complicated than the polling > actually, as it needs to involve total conversion time which may > vary depending on the number of enabled channels. I will see what > would be safer and easier and apply that in v2. > It isn't that complex; we have done it in other drivers. It is less costly and has less overhead than extra i2c read operation(s). Thanks, Guenter
