On Thu, 13 Aug 2020 at 13:24, Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote: > > On Thu, Aug 13, 2020 at 2:14 PM Crt Mori <cmo@xxxxxxxxxxx> wrote: > > > > On Thu, 13 Aug 2020 at 13:03, Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote: > > > > > > On Thu, Aug 13, 2020 at 10:53 AM Crt Mori <cmo@xxxxxxxxxxx> wrote: > > > > > > > > Reduce number of lines and improve readability to convert polling while > > > > loops to do-while. The iopoll.h interface was not used, because we > > > > require more than 20ms timeout, because time for sensor to perform a > > > > measurement is around 10ms and it needs to perform measurements for each > > > > channel (which currently is 3). > > > > > > I don't see how it prevents using iopoll.h. It uses usleep_range() > > > under the hood in the same way you did here, but open coded. > > > > > > > One loop is indeed 10ms and that is not the problem, the problem is > > that timeout is at least 3 calls of this data ready (3 channels), so > > that is at minimum 30ms of timeout, or it could even be 4 in worse > > case scenario and that is outside of the range for usleep to measure. > > So in case of the other loop, where we wait 200ms for channel refresh > > it is also out of scope. Timeout should be in number of tries or in > > msleep range if you ask me. > > I still didn't buy it. You have in both cases usleep_range(). Why in > your case it's okay and in regmap_read_poll_timeout() is not? > I tried and it did not work, so then I read the manual. Looking into * regmap_read_poll_timeout_atomic - Poll until a condition is met or a timeout occurs ... * @delay_us: Time to udelay between reads in us (0 tight-loops). * Should be less than ~10us since udelay is used * (see Documentation/timers/timers-howto.rst). * @timeout_us: Timeout in us, 0 means never timeout So I went to read Documentation/timers/timers-howto.rst SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms): * Use usleep_range - Why not msleep for (1ms - 20ms)? Explained originally here: http://lkml.org/lkml/2007/8/3/250 msleep(1~20) may not do what the caller intends, and will often sleep longer (~20 ms actual sleep for any value given in the 1~20ms range). In many cases this is not the desired behavior. Since I am above the 20ms range, it is too much for usleep_range and that proved to be a case as I got -ETIMEOUT and the desired channels were not read. > > > ... > > > > > > > - while (tries-- > 0) { > > > > + do { > > > > ret = regmap_read(data->regmap, MLX90632_REG_STATUS, > > > > ®_status); > > > > if (ret < 0) > > > > return ret; > > > > - if (reg_status & MLX90632_STAT_DATA_RDY) > > > > - break; > > > > usleep_range(10000, 11000); > > > > - } > > > > + } while (!(reg_status & MLX90632_STAT_DATA_RDY) && tries--); > > > > > > > > if (tries < 0) { > > > > dev_err(&data->client->dev, "data not ready"); > > -- > With Best Regards, > Andy Shevchenko
