Message-ID: <20210309001527.i7fsbevd7xbwwwu2@pop-os.localdomain>
Date:   Tue, 9 Mar 2021 00:15:27 +0000
From:   Joe Sandom <joe.g.sandom@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND][PATCH v4 1/2] Added AMS tsl2591 driver implementation

Thanks for the feedback Andy, just finishing up V5 with the majority of
your comments on board. Some points of clarification inline.

On Mon, Mar 01, 2021 at 01:49:49PM +0200, Andy Shevchenko wrote:
> On Sat, Feb 27, 2021 at 6:58 PM Jonathan Cameron <jic23@...nel.org> wrote:
> > On Mon, 22 Feb 2021 21:23:12 +0000
> > Joe Sandom <joe.g.sandom@...il.com> wrote:
> 
> I will give my review on top of Jonathan's ones.
> 
> ...
> 
> > > Datasheet Available at: https://ams.com/tsl25911
> 
> Can we use Datasheet tag, please?
> 
> Datasheet: <URL>
> 
> > >
> 
> ...and drop this blank line.
> 
> > > Signed-off-by: Joe Sandom <joe.g.sandom@...il.com>
> 
> ...
> 
> > > +config TSL2591
> > > +        tristate "TAOS TSL2591 ambient light sensor"
> > > +        depends on I2C
> > > +        help
> > > +          Select Y here for support of the AMS/TAOS TSL2591 ambient light sensor,
> > > +          featuring channels for combined visible + IR intensity and lux illuminance.
> > > +          Access als data via iio and sysfs. Supports iio_events.
> 
> "Access data via IIO ad sysfs."
> 
> > > +          To compile this driver as a module, select M: the
> > > +          module will be called tsl2591.
> 
> ...
> 
> > > +/* ALS integration time field value to als time*/
> 
> Besides missing space the phrase confuses me (mostly due to "ALS ...
> als..." passage).
> 
> > > +#define TSL2591_FVAL_TO_ATIME(x) (((x) + 1) * 100)
> 
> ...
> 
> > > +/* TSL2591 command register definitions */
> > > +#define TSL2591_CMD_NOP             (BIT(5) | BIT(7))
> > > +#define TSL2591_CMD_SF_INTSET       (BIT(2) | GENMASK(7, 5))
> > > +#define TSL2591_CMD_SF_CALS_I       (BIT(0) | BIT(2) | GENMASK(7, 5))
> > > +#define TSL2591_CMD_SF_CALS_NPI     (GENMASK(2, 0) | GENMASK(7, 5))
> > > +#define TSL2591_CMD_SF_CNP_ALSI     (BIT(1) | BIT(3) | GENMASK(7, 5))
> 
> If it's a bit combination, describe each bit field separately, but my
> guts are telling me that BIT() and GENMASK() use here is wrong.
> 
> ...
> 
> > > +/* TSL2591 enable register definitions */
> > > +#define TSL2591_PWR_ON              BIT(0)
> > > +#define TSL2591_PWR_OFF             0x00
> 
> Similar to above, here you rather use (1 << 0) and (0 << 0), or plain numbers.
> 
> ...
> 
> > > +#define TSL2591_CTRL_ALS_INTEGRATION_100MS  0x00
> > > +#define TSL2591_CTRL_ALS_INTEGRATION_200MS  BIT(0)
> > > +#define TSL2591_CTRL_ALS_INTEGRATION_300MS  BIT(1)
> > > +#define TSL2591_CTRL_ALS_INTEGRATION_400MS  GENMASK(1, 0)
> > > +#define TSL2591_CTRL_ALS_INTEGRATION_500MS  BIT(2)
> > > +#define TSL2591_CTRL_ALS_INTEGRATION_600MS  (BIT(0) | BIT(2))
> 
> Similar to the above. Drop all BIT() / GENMASK() use here and convert
> to plain numbers.
> 
> ...
> 
> > > +#define TSL2591_CTRL_ALS_LOW_GAIN           0x00
> > > +#define TSL2591_CTRL_ALS_MED_GAIN           BIT(4)
> > > +#define TSL2591_CTRL_ALS_HIGH_GAIN          BIT(5)
> 
> Ditto. And so on. Please, revisit all descriptions above and below.
> 
> ...
> 
> > > +#define TSL2591_ALS_MAX_VALUE               65535
> 
> If it's limited by the amount of bits in use, I prefer to spell it as
> (BIT(16) - 1), and we will immediately see this implication.
> 
> ...
> 
> > > +/*
> > > + * Period table is ALS persist cycle x integration time setting
> > > + * Integration times: 100ms, 200ms, 300ms, 400ms, 500ms, 600ms
> > > + * ALS cycles: 1, 2, 3, 5, 10, 20, 25, 30, 35, 40, 45, 50, 55, 60
> > > + */
> > > +static const char * const tsl2591_als_period_list[] = {
> > > +     "0.1 0.2 0.3 0.5 1.0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0",
> > > +     "0.2 0.4 0.6 1.0 2.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0",
> > > +     "0.3 0.6 0.9 1.5 3.0 6.0 7.5 9.0 10.5 12.0 13.5 15.0 16.5 18.0",
> > > +     "0.4 0.8 1.2 2.0 4.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0",
> > > +     "0.5 1.0 1.5 2.5 5.0 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0",
> > > +     "0.6 1.2 1.8 3.0 6.0 12.0 15.0 18.0 21.0 24.0 27.0 30.0 33.0 36.0",
> > > +};
> 
> Okay... But it can be generated I guess.
> 
> ...
> 
> > > +static int tsl2591_als_time_to_fval(const u32 als_integration_time)
> > > +{
> > > +     int i;
> > > +
> > > +     for (i = 0; i < ARRAY_SIZE(tsl2591_int_time_available); ++i) {
> > > +             if (als_integration_time == tsl2591_int_time_available[i])
> > > +                     return ((als_integration_time / 100) - 1);
> 
> Looks like a reversed function of a macro you have above. Care to
> introduce a counterpart macro instead and use it here?
> 
Fair point, counterpart is cleaner - added in v5.

> > > +             if (i == (ARRAY_SIZE(tsl2591_int_time_available) - 1))
> > > +                     break;
> 
> This doesn't make any sense to me.
> 
Looking back at this, definitely no need for it - thanks!

> > > +     }
> > > +
> > > +     return -EINVAL;
> > > +}
> 
> ...
> 
> > > +static int tsl2591_wait_adc_complete(struct tsl2591_chip *chip)
> > > +{
> > > +     struct i2c_client *client = chip->client;
> > > +     struct tsl2591_als_settings settings = chip->als_settings;
> 
> > > +     int delay = TSL2591_FVAL_TO_ATIME(settings.als_int_time);
> 
> Move the assignment closer to the conditional below.
> 
> > > +     int ret;
> > > +     int i;
> > > +
> > > +     if (!delay)
> > > +             return -EINVAL;
> > > +
> > > +     /*
> > > +      * Sleep for ALS integration time to allow enough time
> > > +      * for an ADC read cycle to complete. Check status after
> > > +      * delay for ALS valid
> 
> Missed period.
> 
> > > +      */
> > > +     msleep(delay);
> > > +
> > > +     /* Check for status ALS valid flag for up to 100ms */
> > > +     for (i = 0; i < TSL2591_ALS_STS_VALID_COUNT; ++i) {
> 
> i++ works perfectly.
> 
> > > +             ret = i2c_smbus_read_byte_data(client,
> > > +                                            TSL2591_CMD_NOP | TSL2591_STATUS);
> > > +             if (ret < 0) {
> > > +                     dev_err(&client->dev, "Failed to read register\n");
> > > +                     return -EINVAL;
> > > +             }
> > > +             ret = FIELD_GET(TSL2591_STS_ALS_VALID_MASK, ret);
> > > +             if (ret == TSL2591_STS_VAL_HIGH_MASK)
> > > +                     break;
> > > +
> > > +             if (i == (TSL2591_ALS_STS_VALID_COUNT - 1))
> 
> In many cases you added too many parentheses. It's not a LISP language :-)
> 
> > > +                     return -ENODATA;
> > > +
> > > +             usleep_range(9000, 10000);
> > > +     }
> 
> This can be done using iopoll.h and readx_poll_timeout() helper.
>
> > > +     return 0;
> > > +}
> 
> ...
> 
> > > +static int tsl2591_read_channel_data(struct iio_dev *indio_dev,
> > > +                                  struct iio_chan_spec const *chan,
> > > +                                  int *val, int *val2)
> > > +{
> > > +     struct tsl2591_chip *chip = iio_priv(indio_dev);
> > > +     struct tsl2591_als_settings *settings = &chip->als_settings;
> > > +     struct i2c_client *client = chip->client;
> > > +     int ret;
> > > +     u8 als_data[TSL2591_NUM_DATA_REGISTERS];
> 
> Try to keep reversed xmas tree order in the definition block(s).
>
Didn't consider this before, does look cleaner after all!
> > > +
> 
> This should not be here.
> 
> > > +     int counts_per_lux;
> > > +     int lux;
> > > +     int gain_multi;
> > > +     int int_time_fval;
> 
> > > +
> 
> Ditto.
> 
> > > +     u16 als_ch0;
> > > +     u16 als_ch1;
> > > +
> > > +     ret = tsl2591_wait_adc_complete(chip);
> > > +     if (ret < 0) {
> > > +             dev_err(&client->dev, "No data available. Err: %d\n", ret);
> > > +             return ret;
> > > +     }
> > > +
> > > +     ret = i2c_smbus_read_i2c_block_data(client,
> > > +                                         TSL2591_CMD_NOP | TSL2591_C0_DATAL,
> > > +                                         sizeof(als_data), als_data);
> > > +     if (ret < 0) {
> > > +             dev_err(&client->dev, "Failed to read data bytes");
> > > +                     return ret;
> > For comment below if (ret), that won't work on these calls because IIRC they
> > return the number of bytes transferred.  However, you can move the check locally
> > that this is the right length and ensure 0 is returned for the good path.
> > > +     }
> 
> > > +     als_ch0 = le16_to_cpup((const __le16 *)&als_data[0]);
> > > +     als_ch1 = le16_to_cpup((const __le16 *)&als_data[2]);
> 
> The casting looks wrong. Why do you need it? Perhaps your type of
> als_data is not okay? Or perhaps you need to use get_unaligned_le16()?
> I dunno.
> 
Yep, get_unaligned_le16() works better here.

> > > +     switch (chan->type) {
> > > +     case IIO_INTENSITY:
> > > +             if (chan->channel2 == IIO_MOD_LIGHT_BOTH)
> > > +                     *val = als_ch0;
> > > +             else if (chan->channel2 == IIO_MOD_LIGHT_IR)
> > > +                     *val = als_ch1;
> > > +             else
> > > +                     return -EINVAL;
> > > +             break;
> > > +     case IIO_LIGHT:
> > > +             gain_multi = tsl2591_gain_to_multiplier(settings->als_gain);
> > > +             if (gain_multi < 0) {
> > > +                     dev_err(&client->dev, "Invalid multiplier");
> > > +                     return gain_multi;
> > > +             }
> > > +
> > > +             int_time_fval = TSL2591_FVAL_TO_ATIME(settings->als_int_time);
> > > +             /* Calculate counts per lux value */
> 
> > > +             counts_per_lux =
> > > +                     (int_time_fval * gain_multi) / TSL2591_LUX_COEFFICIENT;
> 
> One line.
> 
> > > +             dev_dbg(&client->dev, "Counts Per Lux: %d\n", counts_per_lux);
> 
> > > +             /* Calculate lux value */
> > > +             lux = ((als_ch0 - als_ch1) *
> > > +                    (1000 - ((als_ch1 * 1000) / als_ch0))) / counts_per_lux;
> 
> > > +             dev_dbg(&client->dev, "Raw lux calculation: %d\n", lux);
> > > +
> > > +             /* Divide by 1000 to get real lux value before scaling */
> > > +             *val = lux / 1000;
> 
> Doing this before the following one makes precision drop. Or not?
> 
I don't believe so, the first part is just calculating to get the whole 
number and the second part is calculating to get the decimal number.
Maybe this isn't clear from the comments.

> > > +             /* Get the decimal part of lux reading */
> > > +             *val2 = ((lux - (*val * 1000)) * 1000);
> > > +
> > > +             break;
> > > +     default:
> > > +             return -EINVAL;
> > > +     }
> > > +
> > > +     return ret;
> >
> > See above for why: I'd return 0 here
> >
> > > +}
> 
> ...
> 
> > > +     als_lower_l = (als_settings.als_lower_thresh & 0x00FF);
> >
> > Given you are writing these into a byte field, probably better to express those
> > masks as 0xFF.
> 
> u8 type may never be bigger than 255. Masks like that are redundant.
> 
> > > +     als_lower_h = ((als_settings.als_lower_thresh >> 8) & 0x00FF);
> > > +     als_upper_l = (als_settings.als_upper_thresh & 0x00FF);
> > > +     als_upper_h = ((als_settings.als_upper_thresh >> 8) & 0x00FF);
> 
> Ditto.
> 
> ...
> 
> > > +static int tsl2591_write_raw(struct iio_dev *indio_dev,
> > > +                          struct iio_chan_spec const *chan,
> > > +                          int val, int val2, long mask)
> > > +{
> > > +     struct tsl2591_chip *chip = iio_priv(indio_dev);
> > > +
> > > +     u8 gain;
> > > +     u32 int_time;
> > > +     int ret;
> 
> No need for power management?
> 
Power management for the chip is just to power on the oscillators
and enable the ALS channel reads. That's why it's only currently done
in tsl2591_read_raw. I don't think it's needed for configuring
integration time and gain etc - it seems to have worked so far :)

> > > +     mutex_lock(&chip->als_mutex);
> 
> > > +     mutex_unlock(&chip->als_mutex);
> > > +     return ret;
> > > +}
> 
> ...
> 
> > > +static int tsl2591_read_event_value(struct iio_dev *indio_dev,
> > > +                                 const struct iio_chan_spec *chan,
> > > +                                 enum iio_event_type type,
> > > +                                 enum iio_event_direction dir,
> > > +                                 enum iio_event_info info, int *val,
> > > +                                 int *val2)
> 
> Ditto.
> 
> ...
> 
> > > +static int __maybe_unused tsl2591_resume(struct device *dev)
> > > +{
> > > +     struct iio_dev *indio_dev = dev_get_drvdata(dev);
> > > +     struct tsl2591_chip *chip = iio_priv(indio_dev);
> > > +     int ret;
> > > +     int power_state;
> > > +
> > > +     if (chip->events_enabled)
> 
> > > +             power_state = TSL2591_PWR_ON |
> > > +                           TSL2591_ENABLE_ALS_INT |
> > > +                           TSL2591_ENABLE_ALS;
> 
> At least the last two can be on one line.
> 
> > > +     else
> > > +             power_state = TSL2591_PWR_ON | TSL2591_ENABLE_ALS;
> > > +
> > > +     mutex_lock(&chip->als_mutex);
> > > +     ret = tsl2591_set_power_state(chip, power_state);
> > > +     mutex_unlock(&chip->als_mutex);
> > > +
> > > +     return ret;
> > > +}
> 
> ...
> 
> > > +static const struct dev_pm_ops tsl2591_pm_ops = {
> > > +     SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> > > +                             pm_runtime_force_resume)
> 
> One line?
> 
> > > +     SET_RUNTIME_PM_OPS(tsl2591_suspend, tsl2591_resume, NULL)
> > > +};
> 
> ...
> 
> > > +static irqreturn_t tsl2591_event_handler(int irq, void *private)
> > > +{
> 
> > > +     /* Clear ALS irq */
> > > +     ret = i2c_smbus_write_byte(client, TSL2591_CMD_SF_CALS_NPI);
> > > +     if (ret < 0)
> 
> > > +             dev_err(&client->dev, "Failed to clear als irq\n");
> 
> In the IRQ handler? Hmm... It potentially floods the logs.
> 
Yep, potentially dangerous - will remove for V5.

> > > +     return IRQ_HANDLED;
> > > +}
> 
> ...
> 
> > > +static const struct of_device_id tsl2591_of_match[] = {
> > > +     { .compatible = "amstaos,tsl2591"},
> 
> > > +     {},
> 
> Comma is not needed on the terminator line.
> 
> > > +};
> 
> -- 
> With Best Regards,
> Andy Shevchenko

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