Re: [PATCH v10] iio: hrtimer: Allow sub Hz granularity

[Jonathan Cameron <jic23@kernel.org>]

On Tue,  9 Mar 2021 13:30:39 -0800
Gwendal Grignou <gwendal@chromium.org> wrote:

> Allow setting frequency below 1Hz or sub 1Hz precision.
> Useful for slow sensors like ALS.
> 
> Test frequency is set properly:
> modprobe iio-trig-hrtimer && \
> mkdir /sys/kernel/config/iio/triggers/hrtimer/t1 && \
> cd /sys/bus/iio/devices/triggerX ;
> for i in 1 .1 .01 .001 ; do
>   echo $i > sampling_frequency
>   cat sampling_frequency
> done
> 
> Signed-off-by: Gwendal Grignou <gwendal@chromium.org>

I'd already picked up v9.
Your follow up fixup patch dealt with the accidental kerneldoc.
So I think everything is good now.

Thanks,

Jonathan

> ---
> Changes since v9:
> - Remove kernel-doc mark in file header comment to fix a kernel test
> robot warning:
> "warning: expecting prototype for O periodic hrtimer trigger driver().
> Prototype was for PSEC_PER_SEC() instead"
> 
> Changes since v8:
> - Define PSEC_PER_SEC locally to avoid dependency
> - Add units of expressions in comment.
> 
> Changes since v7:
> - Check for sign properly, only allow positive frequencies.
> - Return proper error code when input frequency is negative.
> 
> Changes since v6:
> - Check for sign, only allow positive frequencies.
> 
> Changes since v5:
> - Properly support do_div on 32bit architecture: quotient must be u64, dividend
>   u32.
> - Use PSEC_PER_SEC from
>   https://patchwork.kernel.org/project/linux-iio/patch/20210112153709.1074-1-andriy.shevchenko@linux.intel.com/
> 
> Changes since v4:
> - Use do_div() properly.
> 
> Changes since v3:
> - Fix rebasing issue.
> 
> Changes since v2:
> - Add do_div to allow divide by a u64 on 32bit machines.
> 
> Changes since v1:
> - Added documentation.
> 
>  Documentation/iio/iio_configfs.rst     |  1 +
>  drivers/iio/trigger/iio-trig-hrtimer.c | 35 ++++++++++++++++++--------
>  2 files changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/Documentation/iio/iio_configfs.rst b/Documentation/iio/iio_configfs.rst
> index 3a5d76f9e2b97..09845fe525e84 100644
> --- a/Documentation/iio/iio_configfs.rst
> +++ b/Documentation/iio/iio_configfs.rst
> @@ -99,3 +99,4 @@ Each trigger can have one or more attributes specific to the trigger type.
>  
>  "hrtimer" trigger type doesn't have any configurable attribute from /config dir.
>  It does introduce the sampling_frequency attribute to trigger directory.
> +That attribute sets the polling frequency in Hz, with mHz precision.
> diff --git a/drivers/iio/trigger/iio-trig-hrtimer.c b/drivers/iio/trigger/iio-trig-hrtimer.c
> index 410de837d0417..e68a2c56d4593 100644
> --- a/drivers/iio/trigger/iio-trig-hrtimer.c
> +++ b/drivers/iio/trigger/iio-trig-hrtimer.c
> @@ -1,5 +1,5 @@
>  // SPDX-License-Identifier: GPL-2.0-only
> -/**
> +/*
>   * The industrial I/O periodic hrtimer trigger driver
>   *
>   * Copyright (C) Intuitive Aerial AB
> @@ -16,13 +16,16 @@
>  #include <linux/iio/trigger.h>
>  #include <linux/iio/sw_trigger.h>
>  
> +/* Defined locally, not in time64.h yet. */
> +#define PSEC_PER_SEC   1000000000000LL
> +
>  /* default sampling frequency - 100Hz */
>  #define HRTIMER_DEFAULT_SAMPLING_FREQUENCY 100
>  
>  struct iio_hrtimer_info {
>  	struct iio_sw_trigger swt;
>  	struct hrtimer timer;
> -	unsigned long sampling_frequency;
> +	int sampling_frequency[2];
>  	ktime_t period;
>  };
>  
> @@ -38,7 +41,9 @@ ssize_t iio_hrtimer_show_sampling_frequency(struct device *dev,
>  	struct iio_trigger *trig = to_iio_trigger(dev);
>  	struct iio_hrtimer_info *info = iio_trigger_get_drvdata(trig);
>  
> -	return snprintf(buf, PAGE_SIZE, "%lu\n", info->sampling_frequency);
> +	return iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO,
> +			ARRAY_SIZE(info->sampling_frequency),
> +			info->sampling_frequency);
>  }
>  
>  static
> @@ -48,18 +53,26 @@ ssize_t iio_hrtimer_store_sampling_frequency(struct device *dev,
>  {
>  	struct iio_trigger *trig = to_iio_trigger(dev);
>  	struct iio_hrtimer_info *info = iio_trigger_get_drvdata(trig);
> -	unsigned long val;
> -	int ret;
> +	unsigned long long val;
> +	u64 period;
> +	int integer, fract, ret;
>  
> -	ret = kstrtoul(buf, 10, &val);
> +	ret = iio_str_to_fixpoint(buf, 100, &integer, &fract);
>  	if (ret)
>  		return ret;
> +	if (integer < 0 || fract < 0)
> +		return -ERANGE;
> +
> +	val = fract + 1000 * integer;  /* mHz */
>  
> -	if (!val || val > NSEC_PER_SEC)
> +	if (!val || val > UINT_MAX)
>  		return -EINVAL;
>  
> -	info->sampling_frequency = val;
> -	info->period = NSEC_PER_SEC / val;
> +	info->sampling_frequency[0] = integer;  /* Hz */
> +	info->sampling_frequency[1] = fract * 1000;  /* uHz */
> +	period = PSEC_PER_SEC;
> +	do_div(period, val);
> +	info->period = period;  /* nS */
>  
>  	return len;
>  }
> @@ -135,8 +148,8 @@ static struct iio_sw_trigger *iio_trig_hrtimer_probe(const char *name)
>  	hrtimer_init(&trig_info->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
>  	trig_info->timer.function = iio_hrtimer_trig_handler;
>  
> -	trig_info->sampling_frequency = HRTIMER_DEFAULT_SAMPLING_FREQUENCY;
> -	trig_info->period = NSEC_PER_SEC / trig_info->sampling_frequency;
> +	trig_info->sampling_frequency[0] = HRTIMER_DEFAULT_SAMPLING_FREQUENCY;
> +	trig_info->period = NSEC_PER_SEC / trig_info->sampling_frequency[0];
>  
>  	ret = iio_trigger_register(trig_info->swt.trigger);
>  	if (ret)