From: Eva Rachel Retuya <eraretuya@gmail.com>
To: Jonathan Cameron <jic23@kernel.org>
Cc: linux-iio@vger.kernel.org, knaack.h@gmx.de, lars@metafoo.de,
pmeerw@pmeerw.net, dmitry.torokhov@gmail.com,
michael.hennerich@analog.com, daniel.baluta@gmail.com,
amsfield22@gmail.com, florian.vaussard@heig-vd.ch,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/4] iio: accel: adxl345_core: Introduce set_mode and data_ready functions
Date: Wed, 10 May 2017 21:07:35 +0800 [thread overview]
Message-ID: <20170510130733.GA5456@Socrates-UM> (raw)
In-Reply-To: <07a80519-2f22-5974-b03a-8d8aff2f2f07@kernel.org>
On Tue, May 02, 2017 at 05:32:07PM +0100, Jonathan Cameron wrote:
> On 02/05/17 12:39, Eva Rachel Retuya wrote:
> > On Mon, May 01, 2017 at 01:22:52AM +0100, Jonathan Cameron wrote:
> > Hello Jonathan,
> > [...]
> >>> +static int adxl345_set_mode(struct adxl345_data *data, u8 mode)
> >>> +{
> >>> + struct device *dev = regmap_get_device(data->regmap);
> >>> + int ret;
> >>> +
> >>> + ret = regmap_write(data->regmap, ADXL345_REG_POWER_CTL, mode);
> >>> + if (ret < 0) {
> >>> + dev_err(dev, "Failed to set power mode, %d\n", ret);
> >>> + return ret;
> >> drop the return ret here and just return ret at the end of the function.
> >> One of the static checkers will probably moan about this otherwise.
> >
> > OK.
> >
> >>> + }
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +static int adxl345_data_ready(struct adxl345_data *data)
> >>> +{
> >> So this is a polling the dataready bit. Will ensure we always
> >> get fresh data when a read occurs. Please add a comment to
> >> that effect as that's not always how devices work.
> >
> > OK.
> >
> >>> + struct device *dev = regmap_get_device(data->regmap);
> >>> + int tries = 5;
> >>> + u32 val;
> >>> + int ret;
> >>> +
> >>> + do {
> >>> + /*
> >>> + * 1/ODR + 1.1ms; 11.1ms at ODR of 0.10 Hz
> >>> + * Sensor currently operates at default ODR of 100 Hz
> >>> + */
> >>> + usleep_range(1100, 11100);
> >> That's a huge range to allow... I'm not following the argument for why.
> >> Or do we have a stray 0?
> >>
> >
> > Not a stray 0. Range is from 1.1ms to 11.1ms, this represents the
> > wake-up time when going to standby/other power saving modes ->
> > measurement mode. I'm going to clarify the comment on why it is needed
> > on the next revision.
> The point about a range sleep is to allow the kernel flexibility in scheduling
> so as to avoid waking the processor from lower power states when high precision is
> not needed.
>
> If the thing you are talking about needs the maximum time sometimes then you
> should set the minimum value to that and add a bit to avoid unnecessary processor
> wake ups.
Thank you for explaining it. I will keep this in mind while working on
the 3rd revision.
Eva
next prev parent reply other threads:[~2017-05-10 13:08 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-29 7:48 [PATCH v2 0/4] iio: accel: adxl345: Add support for buffered readings Eva Rachel Retuya
2017-04-29 7:48 ` [PATCH v2 1/4] dt-bindings: iio: accel: adxl345: Add optional interrupt-names support Eva Rachel Retuya
2017-04-29 7:48 ` [PATCH v2 2/4] iio: accel: adxl345_core: Introduce set_mode and data_ready functions Eva Rachel Retuya
2017-05-01 0:22 ` Jonathan Cameron
2017-05-01 19:42 ` Andy Shevchenko
2017-05-01 19:48 ` Jonathan Cameron
2017-05-01 20:07 ` Andy Shevchenko
2017-05-01 20:18 ` Jonathan Cameron
2017-05-02 11:39 ` Eva Rachel Retuya
2017-05-02 16:32 ` Jonathan Cameron
2017-05-10 13:07 ` Eva Rachel Retuya [this message]
2017-05-01 11:21 ` Andy Shevchenko
2017-05-02 11:46 ` Eva Rachel Retuya
2017-04-29 7:49 ` [PATCH v2 3/4] iio: accel: adxl345: Setup DATA_READY trigger Eva Rachel Retuya
2017-05-01 0:32 ` Jonathan Cameron
2017-05-02 3:01 ` Rob Herring
2017-05-02 15:59 ` Jonathan Cameron
2017-05-10 14:33 ` Eva Rachel Retuya
2017-05-02 11:59 ` Eva Rachel Retuya
2017-05-01 11:31 ` Andy Shevchenko
2017-05-02 12:15 ` Eva Rachel Retuya
2017-05-02 21:05 ` Andy Shevchenko
2017-05-10 13:24 ` Eva Rachel Retuya
2017-05-14 15:15 ` Jonathan Cameron
2017-05-14 16:08 ` Dmitry Torokhov
2017-05-05 18:26 ` Jonathan Cameron
2017-05-10 13:31 ` Eva Rachel Retuya
2017-04-29 7:49 ` [PATCH v2 4/4] iio: accel: adxl345: Add support for triggered buffer Eva Rachel Retuya
2017-05-01 0:42 ` Jonathan Cameron
2017-05-02 12:23 ` Eva Rachel Retuya
2017-05-02 16:08 ` Jonathan Cameron
2017-05-01 11:24 ` Andy Shevchenko
2017-05-02 12:24 ` Eva Rachel Retuya
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