Messages in this thread | | | Date | Thu, 14 Apr 2022 14:06:56 +0300 | Subject | Re: [PATCH v1 3/3] iio: adc: ad4130: add AD4130 driver | From | Cosmin Tanislav <> |
| |
On 4/13/22 18:41, Andy Shevchenko wrote: > On Wed, Apr 13, 2022 at 1:41 PM Cosmin Tanislav <demonsingur@gmail.com> wrote: > > >> +#include <linux/property.h> >> +#include <linux/regmap.h> >> +#include <linux/regulator/consumer.h> >> +#include <linux/spi/spi.h> >> + >> +#include <linux/iio/iio.h> >> +#include <linux/iio/sysfs.h> > > ... > >> +#define AD4130_8_NAME "ad4130-8" > > What the meaning of -8 ? Is it number of channels? Or is it part of > the official model (part number)? Can we see, btw, Datasheet: tag with > a corresponding link in the commit message? >
That's just the name specified in the datasheet. I honestly don't have much of an idea about why it is like that. Also, I already put the datasheet in the .yaml documentation. Do you really also want it in each commit message too?
> >> +#define AD4130_RESET_CLK_COUNT 64 >> +#define AD4130_RESET_BUF_SIZE (AD4130_RESET_CLK_COUNT / 8) > > To be more precise shouldn't the above need to have DIV_ROUND_UP() ? >
Does it look like 64 / 8 needs any rounding?
> ... > >> +#define AD4130_FREQ_FACTOR 1000000000ull >> +#define AD4130_DB3_FACTOR 1000 > > Ditto.
AD4130_DB3_FACTOR is unit-less. In the datasheet, the relation between sampling frequency and 3db frequency is represented as a 0.xyz value, hence why the db3_div values and 1000 factor.
> >> +enum ad4130_fifo_mode { >> + AD4130_FIFO_MODE_DISABLED = 0b00, >> + AD4130_FIFO_MODE_WATERMARK = 0b01, >> +}; >> + >> +enum ad4130_mode { >> + AD4130_MODE_CONTINUOUS = 0b0000, >> + AD4130_MODE_IDLE = 0b0100, >> +}; > > 0b?! Hmm... Not that this is bad, just not so usual :-) >
I always use 0b to be consistent with the datasheet values which are represented in binary. I think it makes it easier to not mess up when initially translating the datasheet into code and later when cross-checking with the datasheet.
> >> +struct ad4130_filter_config { >> + enum ad4130_filter_mode filter_mode; >> + unsigned int odr_div; >> + unsigned int fs_max; >> + unsigned int db3_div; >> + enum iio_available_type samp_freq_avail_type; >> + int samp_freq_avail_len; >> + int samp_freq_avail[3][2]; >> + enum iio_available_type db3_freq_avail_type; >> + int db3_freq_avail_len; >> + int db3_freq_avail[3][2]; > > These 3:s can be defined? > I could define IIO_AVAIL_RANGE_LEN and IIO_AVAIL_SINGLE_LEN and then define another IIO_AVAIL_LEN that is the max between the two. But that's just over-complicating it, really.
> ... > > >> +static int ad4130_get_reg_size(struct ad4130_state *st, unsigned int reg, >> + unsigned int *size) >> +{ > >> + if (reg >= ARRAY_SIZE(ad4130_reg_size)) >> + return -EINVAL; > > When this condition is true?
When the user tries reading a register from direct_reg_access that hasn't had its size defined.
> >> + regmap_update_bits(st->regmap, AD4130_REG_IO_CONTROL, mask, >> + value ? mask : 0); > > One line? > > No error check? >
I actually can't think of a scenario where this would fail. It doesn't if the chip is not even connected.
> >> + if (setup_info->enabled_channels) >> + return -EINVAL; > > -EBUSY? >
Eh, I don't think so. It would be pretty impossible for the code to hit this if statement, taking into account the ad4130_find_slot() logic. I could as well not have it at all.
> >> +static void ad4130_freq_to_fs(enum ad4130_filter_mode filter_mode, >> + int val, int val2, unsigned int *fs, bool db3) >> +{ >> + const struct ad4130_filter_config *filter_config = >> + &ad4130_filter_configs[filter_mode]; >> + unsigned long long dividend, divisor; >> + int temp; >> + >> + dividend = filter_config->fs_max * filter_config->odr_div * >> + (val * AD4130_FREQ_FACTOR + val2); >> + divisor = AD4130_MAX_ODR * AD4130_FREQ_FACTOR; >> + >> + if (db3) { >> + dividend *= AD4130_DB3_FACTOR; >> + divisor *= filter_config->db3_div; >> + } >> + >> + temp = AD4130_FS_MIN + filter_config->fs_max - >> + DIV64_U64_ROUND_CLOSEST(dividend, divisor); >> + >> + if (temp < AD4130_FS_MIN) >> + temp = AD4130_FS_MIN; >> + else if (temp > filter_config->fs_max) >> + temp = filter_config->fs_max; >> + >> + *fs = temp; > > Would be nice to put a comment explaining the math behind this code. > >> +} >> + >> +static void ad4130_fs_to_freq(enum ad4130_filter_mode filter_mode, >> + unsigned int fs, int *val, int *val2, bool db3) >> +{ >> + const struct ad4130_filter_config *filter_config = >> + &ad4130_filter_configs[filter_mode]; >> + unsigned int dividend, divisor; >> + u64 temp; >> + >> + dividend = (filter_config->fs_max - fs + AD4130_FS_MIN) * >> + AD4130_MAX_ODR; >> + divisor = filter_config->fs_max * filter_config->odr_div; >> + >> + if (db3) { >> + dividend *= filter_config->db3_div; >> + divisor *= AD4130_DB3_FACTOR; >> + } >> + >> + temp = div_u64(dividend * AD4130_FREQ_FACTOR, divisor); >> + *val = div_u64_rem(temp, AD4130_FREQ_FACTOR, val2); > > > Ditto. > I'll see what I can come up with.
> >> + out: > > out_unlock: ? > Ditto for similar cases.
There's a single label in the function, and there's a mutex being taken, and, logically, the mutex must be released on the exit path. It's clear what the label is for to me.
> >> + *val = st->bipolar ? -(1 << (chan->scan_type.realbits - 1)) : 0; > > Hmm... It seems like specific way to have a sign_extended, or actually > reduced) mask. > Can you rewrite it with the (potential)UB-free approach? > > (Note, that if realbits == 32, this will have a lot of fun in > accordance with C standard.) >
Can you elaborate on this? The purpose of this statement is to shift the results so that, when bipolar configuration is enabled, the raw value is offset with 1 << (realbits - 1) towards negative.
For the 24bit chips, 0x800000 becomes 0x000000.
Maybe you misread it as left shift on a negative number? The number is turned negative only after the shift...
> ... > >> + *vals = (int *)st->scale_tbls[setup_info->ref_sel]; > > Can we get rid of casting here and in the similar cases? >
I feel like scale_tbls is best defined as an array of two-element arrays. Because its type is IIO_VAL_FRACTIONAL. But obviously the IIO framework can't take this case into account by itself, so we cast it so it receives what it wants.
> >> + >> + if (val > AD4130_FIFO_SIZE) >> + return -EINVAL; >> + >> + /* >> + * Always set watermark to a multiple of the number of enabled channels >> + * to avoid making the FIFO unaligned. >> + */ >> + eff = rounddown(val, st->num_enabled_channels); >> + >> + mutex_lock(&st->lock); >> + >> + ret = regmap_update_bits(st->regmap, AD4130_REG_FIFO_CONTROL, >> + AD4130_WATERMARK_MASK, >> + FIELD_PREP(AD4130_WATERMARK_MASK, >> + ad4130_watermark_reg_val(eff))); > > Temporary variable for mask? >
You mean for value?
> >> +static int ad4130_get_ref_voltage(struct ad4130_state *st, >> + enum ad4130_ref_sel ref_sel, >> + unsigned int *ref_uv) >> +{ >> + struct device *dev = &st->spi->dev; >> + int ret; >> + >> + switch (ref_sel) { >> + case AD4130_REF_REFIN1: >> + ret = regulator_get_voltage(st->regulators[2].consumer); >> + break; >> + case AD4130_REF_REFIN2: >> + ret = regulator_get_voltage(st->regulators[3].consumer); >> + break; >> + case AD4130_REF_AVDD_AVSS: >> + ret = regulator_get_voltage(st->regulators[0].consumer); >> + break; >> + case AD4130_REF_REFOUT_AVSS: > >> + if (!st->int_ref_en) { >> + ret = -EINVAL; >> + break; >> + } >> + >> + ret = st->int_ref_uv; >> + break; > > Can be one if-else instead. > >> + default: >> + ret = -EINVAL; >> + break; >> + } >> + >> + if (ret <= 0) > > = 0 ?! Can you elaborate, please, this case taking into account below? >
I guess I just did it because voltage = 0 doesn't make sense and would make scale be 0.0.
>> + return dev_err_probe(dev, ret, "Cannot use reference %u\n", >> + ref_sel); >> + >> + if (ref_uv) >> + *ref_uv = ret; >> + >> + return 0; >> +} >
> >> + fwnode_property_read_u32(child, "adi,excitation-pin-0", >> + &chan_info->iout0); > > No default and/or error check? > > ... > >> + fwnode_property_read_u32(child, "adi,excitation-pin-1", >> + &chan_info->iout1); > > Ditto.
Default is 0, just like the register defaults.
> > ... > >> +static int ad4130_parse_fw_children(struct iio_dev *indio_dev) >> +{ >> + struct ad4130_state *st = iio_priv(indio_dev); >> + struct device *dev = &st->spi->dev; >> + struct fwnode_handle *child; >> + int ret; >> + >> + indio_dev->channels = st->chans; >> + >> + device_for_each_child_node(dev, child) { >> + ret = ad4130_parse_fw_channel(indio_dev, child); >> + if (ret) >> + break; >> + } > >> + fwnode_handle_put(child); > > There is no need to put fwnode if child is NULL. Moreover, the above > pattern might be percepted wrongly, i.e. one may think that > fwnode_handle_put() is a must after a loop. >
fwnode_handle_put already checks if the child is NULL. Why do the same check twice?
> > Can you explain why regmap locking is needed? >
Am I supposed to set .disable_locking = true since SPI has its own locking?
| |