Messages in this thread | | | From | Renato Lui Geh <> | Date | Fri, 18 Jan 2019 18:19:40 -0200 | Subject | Re: [PATCH 1/2] staging: iio: ad7780: Add gain & filter gpio support |
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Hi,
Sorry for the (extremely) late reply.
Comments inline.
Renato
On 12/01, Jonathan Cameron wrote: >On Thu, 29 Nov 2018 11:02:46 -0200 >Giuliano Augusto Faulin Belinassi <giuliano.belinassi@usp.br> wrote: > >> Hi > >A few follow ups from me having read the result in patch 2. > >Jonathan >> >> On Thu, Nov 29, 2018 at 9:18 AM Popa, Stefan Serban >> <StefanSerban.Popa@analog.com> wrote: >> > >> > On Mi, 2018-11-28 at 16:15 -0200, Giuliano Belinassi wrote: >> > > Previously, the AD7780 driver only supported gpio for the 'powerdown' >> > > pin. This commit adds suppport for the 'gain' and 'filter' pin. >> > > >> > > Signed-off-by: Giuliano Belinassi <giuliano.belinassi@usp.br> >> > > --- >> > > Changes in v2: >> > > - Now this patch is part of the patchset that aims to remove ad7780 >> > > out of staging. https://marc.info/?l=linux-iio&m=154282349808890&w=2 >> > > - Also, now it reads voltage and filter values from the userspace >> > > instead of gpio pin states. >> > >> > Hello, >> > Please see bellow. >> > >> > > >> > > drivers/staging/iio/adc/ad7780.c | 78 ++++++++++++++++++++++++-- >> > > include/linux/iio/adc/ad_sigma_delta.h | 5 ++ >> > > 2 files changed, 79 insertions(+), 4 deletions(-) >> > > >> > > diff --git a/drivers/staging/iio/adc/ad7780.c >> > > b/drivers/staging/iio/adc/ad7780.c >> > > index c4a85789c2db..05979a79fda3 100644 >> > > --- a/drivers/staging/iio/adc/ad7780.c >> > > +++ b/drivers/staging/iio/adc/ad7780.c >> > > @@ -39,6 +39,12 @@ >> > > #define AD7170_PATTERN (AD7780_PAT0 | AD7170_PAT2) >> > > #define AD7170_PATTERN_MASK (AD7780_PAT0 | AD7780_PAT1 | >> > > AD7170_PAT2) >> > > >> > > +#define AD7780_GAIN_GPIO 0 >> > > +#define AD7780_FILTER_GPIO 1 >> > > + >> > > +#define AD7780_GAIN_MIDPOINT 64 >> > > +#define AD7780_FILTER_MIDPOINT 13350 >> > > + >> > > struct ad7780_chip_info { >> > > struct iio_chan_spec channel; >> > > unsigned int pattern_mask; >> > > @@ -50,6 +56,8 @@ struct ad7780_state { >> > > const struct ad7780_chip_info *chip_info; >> > > struct regulator *reg; >> > > struct gpio_desc *powerdown_gpio; >> > > + struct gpio_desc *gain_gpio; >> > > + struct gpio_desc *filter_gpio; >> > > unsigned int gain; >> > > >> > > struct ad_sigma_delta sd; >> > > @@ -115,18 +123,65 @@ static int ad7780_read_raw(struct iio_dev >> > > *indio_dev, >> > > return -EINVAL; >> > > } >> > > >> > > +static int ad7780_write_raw(struct iio_dev *indio_dev, >> > > + struct iio_chan_spec const *chan, >> > > + int val, >> > > + int val2, >> > > + long m) >> > > +{ >> > > + struct ad7780_state *st = iio_priv(indio_dev); >> > > + const struct ad7780_chip_info *chip_info = st->chip_info; >> > > + int uvref, gain; >> > > + unsigned int full_scale; >> > > + >> > > + if (!chip_info->is_ad778x) >> > > + return 0; >> > > + >> > > + switch (m) { >> > > + case IIO_CHAN_INFO_SCALE: >> > > + if (val != 0) >> > > + return -EINVAL; >> > > + >> > > + uvref = regulator_get_voltage(st->reg); >> > >> > regulator_get_voltage() has already been called in the probe function and >> > the result is stored in st->int_vref_mv. >> >> This was removed in commit 9eae69ddbc4717a0bd702eddac76c7848773bf71 >> because the value was not being updated. But I agree if the vref >> voltage is not going to change at all after the initialization, then >> this value should be kept in memory.
Why wouldn't the vref voltage not change after initialization? Shouldn't we keep reading and updating this in read_raw? >> >> > My suggestion would be to use a local vref variable declared as unsigned >> > int. It is my fault that I haven't explained correctly in the previous >> > email, but you need to multiply vref_mv with 1000000LL in order to get the >> > right precision: vref = st->int_vref_mv * 1000000LL. Afterwards you will be >> > able to perform the divisions.
Shouldn't we read vref inside read_raw in order to get up-to-date readings on voltage values? Or should we keep reading from a cached value? >> >> Thanks for this info! :-) >> Shouldn't we store this in uV (microVolts)? This will yield a more >> accurate result after the multiplication. >> >> > > + >> > > + if (uvref < 0) >> > > + return uvref; >> > > + >> > > + full_scale = 1 << (chip_info->channel.scan_type.realbits >> > > - 1); >> > > + gain = DIV_ROUND_CLOSEST(uvref, full_scale); >> > > + gain = DIV_ROUND_CLOSEST(gain, val2); >> > > + >> > > + gpiod_set_value(st->gain_gpio, gain < >> > > AD7780_GAIN_MIDPOINT ? 0 : 1); >> > >> > Once the gain is set, you can store it in st->gain variable. >> >> Yes, we forgot it. >> >> > >> > > + case IIO_CHAN_INFO_SAMP_FREQ: >> > > + if (val2 != 0) >> > > + return -EINVAL; >comment I raised in patch 2 about the odd preciseness of insisting >no decimal places, but matching any value based on a threshold on the >whole number part.
I see. I thought the filter input was in mHz. So should I compare 1000*val with AD7780_FILTER_MIDPOINT? > >I'd also expect to see read_raw support for this. > >> > > + >> > > + gpiod_set_value(st->filter_gpio, val < >> > > AD7780_FILTER_MIDPOINT ? 0 : 1); >> > >> > This is probably fine, although I am not a big fan of the ternary operator. >> > A simple if else statement would do. However, I don't feel strongly about >> > it, so feel free to disagree. >> > >> > > + break; >> > > + } >> > > + >> > > + return 0; >> > > +} >> > > + >> > > static int ad7780_postprocess_sample(struct ad_sigma_delta *sigma_delta, >> > > unsigned int raw_sample) >> > > { >> > > struct ad7780_state *st = ad_sigma_delta_to_ad7780(sigma_delta); >> > > const struct ad7780_chip_info *chip_info = st->chip_info; >> > > + int val; >> > > >> > > if ((raw_sample & AD7780_ERR) || >> > > ((raw_sample & chip_info->pattern_mask) != chip_info- >> > > >pattern)) >> > > return -EIO; >> > > >> > > if (chip_info->is_ad778x) { >> > > - if (raw_sample & AD7780_GAIN) >> > > + val = raw_sample & AD7780_GAIN; >> > > + >> > > + if (val != gpiod_get_value(st->gain_gpio)) >> > > + return -EIO; >> > >> > It is not obvious to me what is the point of this check. Maybe you can add >> > a comment?
If I'm not mistaken, we had agreed earlier to remove this altogether, as having a redundancy check could potentially slow down reading. >> >> It seems to be a redundancy check. It is getting the 32-bits >> raw_output, getting the bit that represents the GAIN value and >> checking if the pin is set accordingly (see Figure 22 of datasheet, >> page 13). Is this correct? If yes we add a comment explaining this. >> >> > >> > > + >> > > + if (val) >> > > st->gain = 1; >> > > else >> > > st->gain = 128; >> > >> > Do we still need this? I am not convinced. >> No, I don't think so. Thanks for pointing this out :-) >> >> > >> > > @@ -141,18 +196,20 @@ static const struct ad_sigma_delta_info >> > > ad7780_sigma_delta_info = { >> > > .has_registers = false, >> > > }; >> > > >> > > -#define AD7780_CHANNEL(bits, wordsize) \ >> > > +#define AD7170_CHANNEL(bits, wordsize) \ >> > > AD_SD_CHANNEL_NO_SAMP_FREQ(1, 0, 0, bits, 32, wordsize - bits) >> > > +#define AD7780_CHANNEL(bits, wordsize) \ >> > > + AD_SD_CHANNEL_GAIN_FILTER(1, 0, 0, bits, 32, wordsize - bits) >> > > >> > > static const struct ad7780_chip_info ad7780_chip_info_tbl[] = { >> > > [ID_AD7170] = { >> > > - .channel = AD7780_CHANNEL(12, 24), >> > > + .channel = AD7170_CHANNEL(12, 24), >> > > .pattern = AD7170_PATTERN, >> > > .pattern_mask = AD7170_PATTERN_MASK, >> > > .is_ad778x = false, >> > > }, >> > > [ID_AD7171] = { >> > > - .channel = AD7780_CHANNEL(16, 24), >> > > + .channel = AD7170_CHANNEL(16, 24), >> > > .pattern = AD7170_PATTERN, >> > > .pattern_mask = AD7170_PATTERN_MASK, >> > > .is_ad778x = false, >> > > @@ -173,6 +230,7 @@ static const struct ad7780_chip_info >> > > ad7780_chip_info_tbl[] = { >> > > >> > > static const struct iio_info ad7780_info = { >> > > .read_raw = ad7780_read_raw, >> > > + .write_raw = ad7780_write_raw, >> > > }; >> > > >> > > static int ad7780_probe(struct spi_device *spi) >> > > @@ -222,6 +280,18 @@ static int ad7780_probe(struct spi_device *spi) >> > > goto error_disable_reg; >> > > } >> > > >> > > + if (st->chip_info->is_ad778x) { >> > > + st->gain_gpio = devm_gpiod_get_optional(&spi->dev, >> > > + "gain", >> > > + GPIOD_OUT_HIGH); >> > > + if (IS_ERR(st->gain_gpio)) { >> > >> > if the GPIO is optional, then we should continue in case of -ENODEV. >> > >> > Shouldn't we have a devm_gpiod_get_optional() call also for filter_gpio? >I had to check this one... > > * This is equivalent to gpiod_get(), except that when no GPIO was assigned to > * the requested function it will return NULL. This is convenient for drivers > * that need to handle optional GPIOs. > >So nope, it shouldn't return -ENODEV; unlike the clock equivalent which >IIRC does... > >> > >> > > + ret = PTR_ERR(st->gain_gpio); >> > > + dev_err(&spi->dev, "Failed to request gain GPIO: >> > > %d\n", >> > > + ret); >> > > + goto error_disable_reg; >> > > + } >> > > + } >> > > + >> > > ret = ad_sd_setup_buffer_and_trigger(indio_dev); >> > > if (ret) >> > > goto error_disable_reg; >> > > diff --git a/include/linux/iio/adc/ad_sigma_delta.h >> > > b/include/linux/iio/adc/ad_sigma_delta.h >> > > index 730ead1a46df..6cadab6fd5fd 100644 >> > > --- a/include/linux/iio/adc/ad_sigma_delta.h >> > > +++ b/include/linux/iio/adc/ad_sigma_delta.h >> > > @@ -173,6 +173,11 @@ int ad_sd_validate_trigger(struct iio_dev >> > > *indio_dev, struct iio_trigger *trig); >> > > __AD_SD_CHANNEL(_si, _channel, -1, _address, _bits, \ >> > > _storagebits, _shift, NULL, IIO_VOLTAGE, 0) >> > > >> > > +#define AD_SD_CHANNEL_GAIN_FILTER(_si, _channel, _address, _bits, \ >> > > + _storagebits, _shift) \ >> > > + __AD_SD_CHANNEL(_si, _channel, -1, _address, _bits, \ >> > > + _storagebits, _shift, NULL, IIO_VOLTAGE, >> > > BIT(IIO_CHAN_INFO_RAW)) >> > > + >> > > #define AD_SD_TEMP_CHANNEL(_si, _address, _bits, _storagebits, _shift) \ >> > > __AD_SD_CHANNEL(_si, 0, -1, _address, _bits, \ >> > > _storagebits, _shift, NULL, IIO_TEMP, \ >> > >> > -- >> > You received this message because you are subscribed to the Google Groups "Kernel USP" group. >> > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-usp+unsubscribe@googlegroups.com. >> > To post to this group, send email to kernel-usp@googlegroups.com. >> > To view this discussion on the web visit https://groups.google.com/d/msgid/kernel-usp/1543490289.11186.22.camel%40analog.com. >> > For more options, visit https://groups.google.com/d/optout. >
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