From: Crt Mori <firstname.lastname@example.org> To: Andy Shevchenko <email@example.com> Cc: Jonathan Cameron <firstname.lastname@example.org>, linux-iio <email@example.com>, Linux Kernel Mailing List <firstname.lastname@example.org> Subject: Re: [PATCH v5 3/5] iio:temperature:mlx90632: Convert polling while loop to do-while Date: Fri, 14 Aug 2020 11:42:07 +0200 [thread overview] Message-ID: <CAKv63utpidP12iQXWU59=F+cVCq6oShSAitmKhoC4W4aaPtnRA@mail.gmail.com> (raw) In-Reply-To: <CAHp75VfAbufX+jYcxnp8AyAzZ0M42jRCkP5X1sRqXm0jpoyvrQ@mail.gmail.com> On Fri, 14 Aug 2020 at 11:32, Andy Shevchenko <email@example.com> wrote: > > On Fri, Aug 14, 2020 at 10:33 AM Crt Mori <firstname.lastname@example.org> wrote: > > On Thu, 13 Aug 2020 at 21:41, Andy Shevchenko <email@example.com> wrote: > > > On Thu, Aug 13, 2020 at 4:04 PM Crt Mori <firstname.lastname@example.org> wrote: > > > > On Thu, 13 Aug 2020 at 13:24, Andy Shevchenko <email@example.com> wrote: > > > > > On Thu, Aug 13, 2020 at 2:14 PM Crt Mori <firstname.lastname@example.org> wrote: > > > > > > On Thu, 13 Aug 2020 at 13:03, Andy Shevchenko <email@example.com> wrote: > > > > > > > On Thu, Aug 13, 2020 at 10:53 AM Crt Mori <firstname.lastname@example.org> wrote: > > > > > > ... > > > > > > > > > > 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 > > > > > > Why _atomic?! > > > > I just pasted something, it is the same as for non _atomic > > OK. > > ... > > > > > * @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 > > ... > > > > > > > > > usleep_range(10000, 11000); > > > > > > You use here usleep_range(). The same is used for > > > regmap_read_poll_timeout(). What's the difference? > > > > > > Since it uses 1/4 of the range you probably need to update tries and > > > timeout_us to make it work. > > > > > > > Timeout_us here needs to be in one case 100 * 10ms (maybe not > > realistic as we could live with number of around 40 * 10ms), but this > > is a lot more than proposed range of usleep which Is up to 20ms. Even > > in best case this timeout should be 40 ms to give enough time to > > measure 2 channels for sure. So with the current timeout_us > > requirement we are outside of the range of the udelay timer and that > > is why I would need a macro with number of tries, not with the timeout > > value (or timeout value of ms). > > I do not understand. The regmap_read_poll_timeout() is a macro which > unrolls in the very similar loop you have now in the code. > What prevents it from using it? > > I think there is a big misunderstanding about the parameters of that macro. > delay_us (must be small enough), timeout_us can be any long. > I tested on Beaglebone with the 100 * 10000 as timeout_us and I always got the -ETIMEDOUT error. I also tested in the other case where delay_us is 250000 and then timeout_us would be 4*250000 and I have also received -ETIMEDOUT as a response. I can prepare a patch with the iopoll.h API and maybe you will spot the mistake, as after rechecking timeout_us is indeed 64bit and is only used in the time comparison operations and not with timers. > -- > With Best Regards, > Andy Shevchenko
next prev parent reply other threads:[~2020-08-14 9:42 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-08-13 7:51 [PATCH v5 0/5] iio: temperature: mlx90632: Add extended calibration calculations Crt Mori 2020-08-13 7:51 ` [PATCH v5 1/5] iio:temperature:mlx90632: Reduce number of equal calulcations Crt Mori 2020-08-13 7:51 ` [PATCH v5 2/5] iio:temperature:mlx90632: Add kerneldoc to the internal struct Crt Mori 2020-08-13 10:54 ` Andy Shevchenko 2020-08-13 7:51 ` [PATCH v5 3/5] iio:temperature:mlx90632: Convert polling while loop to do-while Crt Mori 2020-08-13 11:03 ` Andy Shevchenko 2020-08-13 11:13 ` Crt Mori 2020-08-13 11:24 ` Andy Shevchenko 2020-08-13 13:03 ` Crt Mori 2020-08-13 19:40 ` Andy Shevchenko 2020-08-14 7:32 ` Crt Mori 2020-08-14 9:31 ` Andy Shevchenko 2020-08-14 9:42 ` Crt Mori [this message] 2020-08-14 12:11 ` Andy Shevchenko 2020-08-13 7:51 ` [PATCH v5 4/5] iio:temperature:mlx90632: Adding extended calibration option Crt Mori 2020-08-13 11:06 ` Andy Shevchenko 2020-08-13 7:51 ` [PATCH v5 5/5] iio:temperature:mlx90632: Some stylefixing leftovers Crt Mori 2020-08-13 11:01 ` Andy Shevchenko 2020-08-13 13:11 ` Crt Mori 2020-08-13 19:41 ` Andy Shevchenko 2020-08-16 8:38 ` Jonathan Cameron
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