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Message-ID: <20220803191621.tzrmndkygfe7nlpx@CAB-WSD-L081021.sigma.sbrf.ru>
Date: Wed, 3 Aug 2022 19:16:13 +0000
From: Dmitry Rokosov <DDRokosov@...rdevices.ru>
To: Andy Shevchenko <andy.shevchenko@...il.com>
CC: "robh+dt@...nel.org" <robh+dt@...nel.org>,
"stano.jakubek@...il.com" <stano.jakubek@...il.com>,
"shawnguo@...nel.org" <shawnguo@...nel.org>,
"jic23@...nel.org" <jic23@...nel.org>,
"lars@...afoo.de" <lars@...afoo.de>,
"stephan@...hold.net" <stephan@...hold.net>,
"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
kernel <kernel@...rdevices.ru>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/3] iio: add MEMSensing MSA311 3-axis accelerometer
driver
Hello Andy,
Thank you for quick review,
On Wed, Aug 03, 2022 at 07:49:33PM +0200, Andy Shevchenko wrote:
> On Wed, Aug 3, 2022 at 3:11 PM Dmitry Rokosov <DDRokosov@...rdevices.ru> wrote:
> >
> > MSA311 is a tri-axial, low-g accelerometer with I2C digital output for
> > sensitivity consumer applications. It has dynamic user-selectable full
> > scales range of +-2g/+-4g/+-8g/+-16g and allows acceleration measurements
> > with output data rates from 1Hz to 1000Hz.
> >
> > Spec: https://cdn-shop.adafruit.com/product-files/5309/MSA311-V1.1-ENG.pdf
> >
> > This driver supports following MSA311 features:
> > - IIO interface
> > - Different power modes: NORMAL and SUSPEND (using pm_runtime)
> > - ODR (Output Data Rate) selection
> > - Scale and samp_freq selection
> > - IIO triggered buffer, IIO reg access
> > - NEW_DATA interrupt + trigger
> >
> > Below features to be done:
> > - Motion Events: ACTIVE, TAP, ORIENT, FREEFALL
> > - Low Power mode
>
> Thanks for an update, my comments below.
>
> ...
>
> > +#include <linux/i2c.h>
>
> > +#include <linux/iio/buffer.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/iio/sysfs.h>
> > +#include <linux/iio/trigger.h>
> > +#include <linux/iio/trigger_consumer.h>
> > +#include <linux/iio/triggered_buffer.h>
>
> I would split this group out of generic headers...
>
> > +#include <linux/mod_devicetable.h>
> > +#include <linux/module.h>
> > +#include <linux/pm.h>
> > +#include <linux/pm_runtime.h>
> > +#include <linux/regmap.h>
> > +#include <linux/string_helpers.h>
> > +#include <linux/units.h>
> > +
>
> ...and move it here to clearly show that the driver belongs to the IIO
> subsystem.
Sure, no problem.
>
> ...
>
> > +/*
> > + * Possible Full Scale ranges
> > + *
> > + * Axis data is 12-bit signed value, so
> > + *
> > + * fs0 = (2 + 2) * 9.81 / (2<<11) = 0.009580
> > + * fs1 = (4 + 4) * 9.81 / (2<<11) = 0.019160
> > + * fs2 = (8 + 8) * 9.81 / (2<<11) = 0.038320
> > + * fs3 = (16 + 16) * 9.81 / (2<<11) = 0.076641
>
> I'm not sure if you are using programming language here or math language?
> In math we refer to powers like 2^11, the 2<<11 puzzles me.
>
Agree, will change in the v5.
> > + */
>
> ...
>
> > +static const struct {
> > + int val;
> > + int val2;
> > +} msa311_fs_table[] = {
> > + {0, 9580}, {0, 19160}, {0, 38320}, {0, 76641}
> > +};
>
> Besides that this struct is defined not only once in the file, this is
> very well NIH struct s32_fract. Why not use the latter?
>
> ...
>
Good point, but looks like this struct is not so popular in the other
kernel drivers:
===
grep "s32_fract" -r -l . | wc -l
3
===
[...]
> > +static const char * const msa311_pwr_modes[] = {
> > + [MSA311_PWR_MODE_NORMAL] = "normal",
> > + [MSA311_PWR_MODE_LOW] = "low",
> > + [MSA311_PWR_MODE_UNKNOWN] = "unknown",
> > + [MSA311_PWR_MODE_SUSPEND] = "suspend"
>
> Leave a comma here even if we know that in the nearest future it won't
> be changed.
>
Good catch, forgot it.
> > +};
>
> ...
>
> > + .cache_type = REGCACHE_RBTREE,
>
> Tree hash is good for sparse data, do you really have it sparse (a lot
> of big gaps in between)?
I suppose so. MSA311 regmap has ~6 gaps.
[...]
>
> > + dev_err(dev,
> > + "failed to set odr %u.%uHz, not available in %s mode\n",
> > + msa311_odr_table[odr].val,
> > + msa311_odr_table[odr].val2 / 1000,
>
> KILO ?
MILLIHZ_PER_HZ :)
>
> > + msa311_pwr_modes[pwr_mode]);
>
> ...
>
> > + static const int unintr_thresh_ms = 20;
>
> You seem not using it as _ms, but always as _us, why not define accordingly?
> Also the other one is defined as unsigned long and this is as int. Why
> not unsigned?
>
> ...
>
I compare unintr_thresh_ms with wait_ms and use wait_ms with
msleep_interruptible(), and I think 20ms is more readable than 20000us
or 20 * USEC_PER_MSEC us.
But I agree about sign. It should be unsigned anyway.
> > + for (fs = 0; fs < ARRAY_SIZE(msa311_fs_table); ++fs)
>
> fs++ will work as well.
>
I would prefer ++fs if you don't mind :)
> > + /* Do not check msa311_fs_table[fs].val, it's always 0 */
> > + if (val2 == msa311_fs_table[fs].val2) {
> > + mutex_lock(&msa311->lock);
> > + err = regmap_field_write(msa311->fields[F_FS], fs);
> > + mutex_unlock(&msa311->lock);
>
> > + if (err)
> > + dev_err(dev, "cannot update scale (%d)\n", err);
>
> This can be done after putting the device back into (auto)sleep, right?
>
Are you talking about dev_err logging? Sure, it can be moved after
pm_runtime* calls.
> > + break;
> > + }
> > +
> > + pm_runtime_mark_last_busy(dev);
> > + pm_runtime_put_autosuspend(dev);
>
> ...
>
> > + for (odr = 0; odr < ARRAY_SIZE(msa311_odr_table); ++odr)
>
> odr++ works well also.
I would prefer ++odr if you don't mind :)
>
> ...
>
> > + dev_err(dev, "cannot update freq (%d)\n", err);
>
> frequency
It will be more ugly due 80 symbols restriction.
>
> ...
>
> > + dev_err(dev, "cannot %s register %u from debugfs (%d)\n",
> > + readval ? "read" : "write", reg, err);
>
> You may consider taking [1] as a precursor here and use str_read_write().
>
> [1]: https://lore.kernel.org/linux-i2c/20220703154232.55549-1-andriy.shevchenko@linux.intel.com/
Oh, really... Thank you for suggestion!
>
> ...
>
> > + struct device *dev = msa311->dev;
>
> Isn't it the same as indio_dev->dev.parent?
> Do you really need that member?
Should be the same... I will check.
>
> ...
>
> > + int bit = 0, err, i = 0;
>
> How is the bit initial assignment used?
You are right, for for_each_set_bit() initializes bit inside.
[...]
> > + dev_dbg(dev, "found MSA311 compatible chip[%#x]\n", partid);
>
> Useless message.
>
Why? It's under dynamic debug, so I will see it if I really want to.
> ...
>
> > + return dev_err_probe(dev, err, "cannot disable set0 intrs\n");
>
> interrupts
It will be more ugly due 80 symbols restriction.
[...]
> > + /* Disable all axis by default */
>
> axis...
>
> > + err = regmap_update_bits(msa311->regs, MSA311_ODR_REG,
> > + MSA311_GENMASK(F_X_AXIS_DIS) |
> > + MSA311_GENMASK(F_Y_AXIS_DIS) |
> > + MSA311_GENMASK(F_Z_AXIS_DIS), 0);
> > + if (err)
> > + return dev_err_probe(dev, err, "cannot enable all axes\n");
>
> ...or axes?
Axes of course.
>
> ...
>
> > + return dev_err_probe(dev, err, "failed to set accel freq\n");
>
> frequency
>
It will be more ugly due 80 symbols restriction.
[...]
> > + return dev_err_probe(dev, -ENOMEM,
> > + "cannot allocate newdata trig\n");
>
> trigger
It will be more ugly due 80 symbols restriction.
[...]
> > + return dev_err_probe(dev, err, "cannot enable push-pull int\n");
>
> interrupt
It will be more ugly due 80 symbols restriction.
> > + indio_dev->modes = 0; /* setup buffered mode later */
>
> Why explicit assignment to 0? Doesn't kzalloc() do it for you?
kzalloc() will do it for me, of course. Previously, I initialized modes to
INDIO_DIRECT_MODE to just provide default value for that. Jonathan
suggested to replace it with 0. I can remove this line at all, no problem.
I just thought, it's more readable.
>
> ...
>
> > + return dev_err_probe(dev, err, "cannot setup iio trig buf\n");
>
> IIO trigger buffer
It will be more ugly due 80 symbols restriction.
>
> ...
>
> > + return dev_err_probe(dev, err, "iio device register failed\n");
>
> IIO
>
> --
> With Best Regards,
> Andy Shevchenko
--
Thank you,
Dmitry
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