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Date:   Sat, 30 Sep 2023 16:42:51 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     David Lechner <dlechner@baylibre.com>
Cc:     linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
        linux-staging@lists.linux.dev,
        David Lechner <david@lechnology.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Michael Hennerich <Michael.Hennerich@analog.com>,
        Nuno =?UTF-8?B?U8Oh?= <nuno.sa@analog.com>,
        Axel Haslam <ahaslam@baylibre.com>,
        Philip Molloy <pmolloy@baylibre.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 22/27] staging: iio: resolver: ad2s1210: convert LOS
 threshold to event attr
Message-ID: <20230930164251.5c07723c@jic23-huawei>
In-Reply-To: <20230929-ad2s1210-mainline-v3-22-fa4364281745@baylibre.com>
References: <20230929-ad2s1210-mainline-v3-0-fa4364281745@baylibre.com>
        <20230929-ad2s1210-mainline-v3-22-fa4364281745@baylibre.com>
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On Fri, 29 Sep 2023 12:23:27 -0500
David Lechner <dlechner@baylibre.com> wrote:

> From: David Lechner <david@lechnology.com>
> 
> From: David Lechner <dlechner@baylibre.com>
> 
> The AD2S1210 has a programmable threshold for the loss of signal (LOS)
> fault. This fault is triggered when either the sine or cosine input
> falls below the threshold voltage.
> 
> This patch converts the custom device LOS threshold attribute to an
> event falling edge threshold attribute on a new monitor signal channel.
> The monitor signal is an internal signal that combines the amplitudes
> of the sine and cosine inputs as well as the current angle and position
> output. This signal is used to detect faults in the input signals.

Hmm. Looking forwards, I'm less sure that we should be shoving all these
error conditions onto one channel. Fundamentally we have
sine and cosine inputs. I think we should treat those as separate channels
and include a third differential channel between them.

So this one becomes a double event (you need to signal it on both
cosine and sine channels).  The DOS overange is similar.
The DOS mismatch is a threshold on the differential channel giving

events/in_altvoltage0_thresh_falling_value
events/in_altvoltage1_thresh_falling_value (these match)
events/in_altvoltage0_thresh_rising_value
events/in_altvoltage1_thresh_rising_value (matches previous which is fine)
events/in_altvoltage1-0_mag_rising_value

Does that work here?  Avoids smashing different types of signals together.
We could even do the LOT as differential between two angle channels
(tracking one and measured one) but meh that's getting complex.

Note this will rely on channel labels to make the above make any sense at all.

Jonathan


> 
> The attribute now uses millivolts instead of the raw register value in
> accordance with the IIO ABI.
> 
> Emitting the event will be implemented in a later patch.
> 
> Signed-off-by: David Lechner <dlechner@baylibre.com>
> ---
> 
> v3 changes: This is a new patch in v3
> 
>  drivers/staging/iio/resolver/ad2s1210.c | 75 +++++++++++++++++++++++++++++++--
>  1 file changed, 71 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
> index 5cc8106800d6..7abbc184c351 100644
> --- a/drivers/staging/iio/resolver/ad2s1210.c
> +++ b/drivers/staging/iio/resolver/ad2s1210.c
> @@ -66,6 +66,11 @@
>  #define PHASE_360_DEG_TO_RAD_INT 6
>  #define PHASE_360_DEG_TO_RAD_MICRO 283185
>  
> +/* Threshold voltage registers have 1 LSB == 38 mV */
> +#define THRESHOLD_MILLIVOLT_PER_LSB 38
> +/* max voltage for threshold registers is 0x7F * 38 mV */
> +#define THRESHOLD_RANGE_STR "[0 38 4826]"
> +
>  enum ad2s1210_mode {
>  	MOD_POS = 0b00,
>  	MOD_VEL = 0b01,
> @@ -448,6 +453,38 @@ static const int ad2s1210_lot_threshold_urad_per_lsb[] = {
>  	1237, /* 16-bit: same as 14-bit */
>  };
>  
> +static int ad2s1210_get_voltage_threshold(struct ad2s1210_state *st,
> +					  unsigned int reg, int *val)
> +{
> +	unsigned int reg_val;
> +	int ret;
> +
> +	mutex_lock(&st->lock);
> +	ret = regmap_read(st->regmap, reg, &reg_val);
> +	mutex_unlock(&st->lock);
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	*val = reg_val * THRESHOLD_MILLIVOLT_PER_LSB;
> +	return IIO_VAL_INT;
> +}
> +
> +static int ad2s1210_set_voltage_threshold(struct ad2s1210_state *st,
> +					  unsigned int reg, int val)
> +{
> +	unsigned int reg_val;
> +	int ret;
> +
> +	reg_val = val / THRESHOLD_MILLIVOLT_PER_LSB;
> +
> +	mutex_lock(&st->lock);
> +	ret = regmap_write(st->regmap, reg, reg_val);
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +}
> +
>  static int ad2s1210_get_lot_high_threshold(struct ad2s1210_state *st,
>  					   int *val, int *val2)
>  {
> @@ -706,9 +743,6 @@ static int ad2s1210_write_raw(struct iio_dev *indio_dev,
>  static IIO_DEVICE_ATTR(fault, 0644,
>  		       ad2s1210_show_fault, ad2s1210_clear_fault, 0);
>  
> -static IIO_DEVICE_ATTR(los_thrd, 0644,
> -		       ad2s1210_show_reg, ad2s1210_store_reg,
> -		       AD2S1210_REG_LOS_THRD);
>  static IIO_DEVICE_ATTR(dos_ovr_thrd, 0644,
>  		       ad2s1210_show_reg, ad2s1210_store_reg,
>  		       AD2S1210_REG_DOS_OVR_THRD);
> @@ -745,6 +779,16 @@ static const struct iio_event_spec ad2s1210_phase_event_spec[] = {
>  	},
>  };
>  
> +static const struct iio_event_spec ad2s1210_monitor_signal_event_spec[] = {
> +	{
> +		/* Sine/cosine below LOS threshold fault. */
> +		.type = IIO_EV_TYPE_THRESH,
> +		.dir = IIO_EV_DIR_FALLING,
> +		/* Loss of signal threshold. */
> +		.mask_separate = BIT(IIO_EV_INFO_VALUE),
> +	},
> +};
> +
>  static const struct iio_chan_spec ad2s1210_channels[] = {
>  	{
>  		.type = IIO_ANGL,
> @@ -803,12 +847,19 @@ static const struct iio_chan_spec ad2s1210_channels[] = {
>  		.scan_index = -1,
>  		.info_mask_separate = BIT(IIO_CHAN_INFO_FREQUENCY),
>  		.info_mask_separate_available = BIT(IIO_CHAN_INFO_FREQUENCY),
> +	}, {
> +		/* monitor signal */
> +		.type = IIO_ALTVOLTAGE,
> +		.indexed = 1,
> +		.channel = 0,
> +		.scan_index = -1,
> +		.event_spec = ad2s1210_monitor_signal_event_spec,
> +		.num_event_specs = ARRAY_SIZE(ad2s1210_monitor_signal_event_spec),
>  	},
>  };
>  
>  static struct attribute *ad2s1210_attributes[] = {
>  	&iio_dev_attr_fault.dev_attr.attr,
> -	&iio_dev_attr_los_thrd.dev_attr.attr,
>  	&iio_dev_attr_dos_ovr_thrd.dev_attr.attr,
>  	&iio_dev_attr_dos_mis_thrd.dev_attr.attr,
>  	&iio_dev_attr_dos_rst_max_thrd.dev_attr.attr,
> @@ -847,11 +898,13 @@ IIO_CONST_ATTR(in_phase0_mag_value_available,
>  	       __stringify(PHASE_44_DEG_TO_RAD_MICRO) " "
>  	       __stringify(PHASE_360_DEG_TO_RAD_INT) "."
>  	       __stringify(PHASE_360_DEG_TO_RAD_MICRO));
> +IIO_CONST_ATTR(in_altvoltage0_thresh_falling_value_available, THRESHOLD_RANGE_STR);
>  IIO_DEVICE_ATTR_RO(in_angl1_thresh_rising_value_available, 0);
>  IIO_DEVICE_ATTR_RO(in_angl1_thresh_rising_hysteresis_available, 0);
>  
>  static struct attribute *ad2s1210_event_attributes[] = {
>  	&iio_const_attr_in_phase0_mag_value_available.dev_attr.attr,
> +	&iio_const_attr_in_altvoltage0_thresh_falling_value_available.dev_attr.attr,
>  	&iio_dev_attr_in_angl1_thresh_rising_value_available.dev_attr.attr,
>  	&iio_dev_attr_in_angl1_thresh_rising_hysteresis_available.dev_attr.attr,
>  	NULL,
> @@ -904,6 +957,13 @@ static int ad2s1210_read_event_value(struct iio_dev *indio_dev,
>  		default:
>  			return -EINVAL;
>  		}
> +	case IIO_ALTVOLTAGE:
> +		if (chan->output)
> +			return -EINVAL;
> +		if (type == IIO_EV_TYPE_THRESH && dir == IIO_EV_DIR_FALLING)
> +			return ad2s1210_get_voltage_threshold(st,
> +						AD2S1210_REG_LOS_THRD, val);
> +		return -EINVAL;
>  	case IIO_PHASE:
>  		return ad2s1210_get_phase_lock_range(st, val, val2);
>  	default:
> @@ -930,6 +990,13 @@ static int ad2s1210_write_event_value(struct iio_dev *indio_dev,
>  		default:
>  			return -EINVAL;
>  		}
> +	case IIO_ALTVOLTAGE:
> +		if (chan->output)
> +			return -EINVAL;
> +		if (type == IIO_EV_TYPE_THRESH && dir == IIO_EV_DIR_FALLING)
> +			return ad2s1210_set_voltage_threshold(st,
> +						AD2S1210_REG_LOS_THRD, val);
> +		return -EINVAL;
>  	case IIO_PHASE:
>  		return ad2s1210_set_phase_lock_range(st, val, val2);
>  	default:
>