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Date:   Thu, 26 Oct 2023 03:15:09 -0700
From:   Sukrut Bellary <sukrut.bellary@linux.com>
To:     Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc:     Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Angelo Compagnucci <angelo.compagnucci@gmail.com>,
        Nishanth Menon <nm@ti.com>, linux-iio@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] iio: adc: ti-adc128s052: Add lower resolution
 devices support
Message-ID: <ZTo8LbMoj/q95CfC@dev-linux.lan>
References: <20231022031203.632153-1-sukrut.bellary@linux.com>
 <20231022031203.632153-3-sukrut.bellary@linux.com>
 <20231022170048.289a1897@jic23-huawei>
 <ZThKqFN6l8HHSXGw@dev-linux.lan>
 <20231025152400.000013e4@Huawei.com>
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On Wed, Oct 25, 2023 at 03:24:00PM +0100, Jonathan Cameron wrote:
> On Tue, 24 Oct 2023 15:52:24 -0700
> Sukrut Bellary <sukrut.bellary@linux.com> wrote:
> 
> > On Sun, Oct 22, 2023 at 05:00:48PM +0100, Jonathan Cameron wrote:
> > > On Sat, 21 Oct 2023 20:12:03 -0700
> > > Sukrut Bellary <sukrut.bellary@linux.com> wrote:
> > >   
> > > > The adcxx4s communicates with a host processor via an SPI/Microwire Bus
> > > > interface. The device family responds with 12-bit data, of which the LSB
> > > > bits are transmitted by the lower resolution devices as 0.
> > > > The unavailable bits are 0 in LSB.
> > > > Shift is calculated per resolution and used in scaling and
> > > > raw data read.
> > > > 
> > > > Lets reuse the driver to support the family of devices with name
> > > > ADC<bb><c>S<sss>, where
> > > > * bb is the resolution in number of bits (8, 10, 12)
> > > > * c is the number of channels (1, 2, 4, 8)
> > > > * sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
> > > > and 101 for 1 MSPS)
> > > > 
> > > > Complete datasheets are available at TI's website here:
> > > > https://www.ti.com/lit/gpn/adc<bb><c>s<sss>.pdf
> > > > 
> > > > Tested only with ti-adc102s051 on BegalePlay SBC.
> > > > https://www.beagleboard.org/boards/beagleplay
> > > > 
> > > > arm64: dts: ti: k3-am625-beagleplay: Add adc102s051
> > > > Add adc102s051 support.
> > > > Tested on beaglePlay SBC
> > > > https://www.beagleboard.org/boards/beagleplay
> > > > 
> > > > Co-developed-by: Nishanth Menon <nm@ti.com>
> > > > Signed-off-by: Nishanth Menon <nm@ti.com>
> > > > Signed-off-by: Sukrut Bellary <sukrut.bellary@linux.com>
> > > > ---
> > > > Changes in v2:
> > > >         - Arranged of_device_id and spi_device_id in numeric order.
> > > >         - Used enum to index into adc128_config.
> > > >         - Reorder adc128_config in alphabetical.
> > > >         - Include channel resolution information.
> > > >         - Shift is calculated per resolution and used in scaling and 
> > > >           raw data read.
> > > > - Link to v1: https://lore.kernel.org/all/20220701042919.18180-3-nm@ti.com/
> > > > ---
> > > >  drivers/iio/adc/ti-adc128s052.c | 131 +++++++++++++++++++++++---------
> > > >  1 file changed, 96 insertions(+), 35 deletions(-)
> > > > 
> > > > diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
> > > > index a456ea78462f..61e3181b8daf 100644
> > > > --- a/drivers/iio/adc/ti-adc128s052.c
> > > > +++ b/drivers/iio/adc/ti-adc128s052.c
> > > > @@ -7,6 +7,22 @@
> > > >   * https://www.ti.com/lit/ds/symlink/adc128s052.pdf
> > > >   * https://www.ti.com/lit/ds/symlink/adc122s021.pdf
> > > >   * https://www.ti.com/lit/ds/symlink/adc124s021.pdf
> > > > + *
> > > > + * The adcxx4s communicates with a host processor via an SPI/Microwire Bus
> > > > + * interface. This driver supports the whole family of devices with a name
> > > > + * ADC<bb><c>S<sss>, where
> > > > + * bb is the resolution in number of bits (8, 10, 12)
> > > > + * c is the number of channels (1, 2, 4, 8)
> > > > + * sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS
> > > > + * and 101 for 1 MSPS)
> > > > + *
> > > > + * Complete datasheets are available at TI's website here:
> > > > + *   https://www.ti.com/lit/gpn/adc<bb><c>s<sss>.pdf
> > > > + *
> > > > + * 8, 10, and 12 bits converters send 12-bit data with
> > > > + * unavailable bits set to 0 in LSB.
> > > > + * Shift is calculated per resolution and used in scaling and
> > > > + * raw data read.
> > > >   */
> > > >  
> > > >  #include <linux/err.h>
> > > > @@ -53,7 +69,7 @@ static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
> > > >  	if (ret < 0)
> > > >  		return ret;
> > > >  
> > > > -	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
> > > > +	return (adc->buffer[0] << 8 | adc->buffer[1]);  
> > > Firstly outer brackets don't add anything.
> > > Secondly, this is an endian conversion.
> > > 
> > > return be16_to_cpu(adc->buffer);
> > > 
> > > should do the job as we know it's aligned enough for a be16.
> > > 
> > >  
> > 
> > Thanks for the review.
> > Yes, I will use be16_to_cpu().
> > 
> > > >  }
> > > >  
> > > >  static int adc128_read_raw(struct iio_dev *indio_dev,
> > > > @@ -70,7 +86,8 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
> > > >  		if (ret < 0)
> > > >  			return ret;
> > > >  
> > > > -		*val = ret;
> > > > +		*val = (ret >> channel->scan_type.shift) &
> > > > +			GENMASK(channel->scan_type.realbits - 1, 0);
> > > >  		return IIO_VAL_INT;
> > > >  
> > > >  	case IIO_CHAN_INFO_SCALE:
> > > > @@ -80,7 +97,7 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
> > > >  			return ret;
> > > >  
> > > >  		*val = ret / 1000;
> > > > -		*val2 = 12;
> > > > +		*val2 = channel->scan_type.realbits;
> > > >  		return IIO_VAL_FRACTIONAL_LOG2;
> > > >  
> > > >  	default:
> > > > @@ -89,24 +106,34 @@ static int adc128_read_raw(struct iio_dev *indio_dev,
> > > >  
> > > >  }
> > > >  
> > > > -#define ADC128_VOLTAGE_CHANNEL(num)	\
> > > > -	{ \
> > > > -		.type = IIO_VOLTAGE, \
> > > > -		.indexed = 1, \
> > > > -		.channel = (num), \
> > > > -		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> > > > -		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) \
> > > > +#define _ADC128_VOLTAGE_CHANNEL(num, real_bits, store_bits)		\
> > > > +	{								\
> > > > +		.type = IIO_VOLTAGE,					\
> > > > +		.indexed = 1,						\
> > > > +		.channel = (num),					\
> > > > +		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
> > > > +		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
> > > > +		.scan_index = (num),					\
> > > > +		.scan_type = {						\
> > > > +			.sign = 'u',					\
> > > > +			.realbits = (real_bits),			\
> > > > +			.storagebits = (store_bits),			\
> > > > +			.shift = (12 - real_bits),			\
> > > > +		},							\
> > > >  	}
> > > >  
> > > > -static const struct iio_chan_spec adc128s052_channels[] = {
> > > > -	ADC128_VOLTAGE_CHANNEL(0),
> > > > -	ADC128_VOLTAGE_CHANNEL(1),
> > > > -	ADC128_VOLTAGE_CHANNEL(2),
> > > > -	ADC128_VOLTAGE_CHANNEL(3),
> > > > -	ADC128_VOLTAGE_CHANNEL(4),
> > > > -	ADC128_VOLTAGE_CHANNEL(5),
> > > > -	ADC128_VOLTAGE_CHANNEL(6),
> > > > -	ADC128_VOLTAGE_CHANNEL(7),
> > > > +#define ADC082_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 8, 16)
> > > > +#define ADC102_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 10, 16)
> > > > +#define ADC128_VOLTAGE_CHANNEL(num) _ADC128_VOLTAGE_CHANNEL(num, 12, 16)
> > > > +
> > > > +static const struct iio_chan_spec adc082s021_channels[] = {
> > > > +	ADC082_VOLTAGE_CHANNEL(0),
> > > > +	ADC082_VOLTAGE_CHANNEL(1),
> > > > +};
> > > > +
> > > > +static const struct iio_chan_spec adc102s021_channels[] = {
> > > > +	ADC102_VOLTAGE_CHANNEL(0),
> > > > +	ADC102_VOLTAGE_CHANNEL(1),
> > > >  };
> > > >  
> > > >  static const struct iio_chan_spec adc122s021_channels[] = {
> > > > @@ -121,10 +148,32 @@ static const struct iio_chan_spec adc124s021_channels[] = {
> > > >  	ADC128_VOLTAGE_CHANNEL(3),
> > > >  };
> > > >  
> > > > +static const struct iio_chan_spec adc128s052_channels[] = {
> > > > +	ADC128_VOLTAGE_CHANNEL(0),
> > > > +	ADC128_VOLTAGE_CHANNEL(1),
> > > > +	ADC128_VOLTAGE_CHANNEL(2),
> > > > +	ADC128_VOLTAGE_CHANNEL(3),
> > > > +	ADC128_VOLTAGE_CHANNEL(4),
> > > > +	ADC128_VOLTAGE_CHANNEL(5),
> > > > +	ADC128_VOLTAGE_CHANNEL(6),
> > > > +	ADC128_VOLTAGE_CHANNEL(7),
> > > > +};
> > > > +
> > > >  static const struct adc128_configuration adc128_config[] = {
> > > > -	{ adc128s052_channels, ARRAY_SIZE(adc128s052_channels) },
> > > > +	{ adc082s021_channels, ARRAY_SIZE(adc082s021_channels) },
> > > > +	{ adc102s021_channels, ARRAY_SIZE(adc102s021_channels) },
> > > >  	{ adc122s021_channels, ARRAY_SIZE(adc122s021_channels) },
> > > >  	{ adc124s021_channels, ARRAY_SIZE(adc124s021_channels) },
> > > > +	{ adc128s052_channels, ARRAY_SIZE(adc128s052_channels) },
> > > > +};
> > > > +
> > > > +/* Ensure match with adc128_config indices */  
> > > 
> > > Make sure that is the case by using them when setting it up.
> > > 
> > > static const struct adc128_configuration adc128_config[] {
> > > 	[ADC128_CONFIG_INDEX_082S] = {
> > > 		adc082s021_channels, ARRAY_SIZE(..) 
> > > 	},
> > > 	[ADC128_CONFIG_INDEX_102S] = ..
> > > }
> > >   
> > 
> > OK, I will use enum while setting it up
> > 
> > +static const struct adc128_configuration adc128_config[] = {
> > +       [ADC128_CONFIG_INDEX_082S] = {
> > +               .channels = adc082s021_channels,
> > +               .num_channels = ARRAY_SIZE(adc082s021_channels)
> > }
> > 
> > Use enum in spi_device_id[]
> > 
> > static const struct spi_device_id adc128_id[] = {
> > +       { "adc082s021", (kernel_ulong_t)ADC128_CONFIG_INDEX_082S },
> > +       { "adc082s051", (kernel_ulong_t)ADC128_CONFIG_INDEX_082S },
> > 
> > }
> > 
> > And use it in probe to extract the config for channels and num_channels using
> > 
> > config = &adc128_config[spi_get_device_id(spi)->driver_data];
> > 
> > since we are not using of_device_id for extracting config, I can remove
> > the .data entry or need to type case it.
> 
> Please don't. That is much more fragile than preferring to get the data
> from the firmware that we matched on.
> 
> We have some IIO drivers doing this but only because we haven't yet updated
> them all yet.
> 
> Jonathan
>

OK, I will keep the of_device_id and spi_device_id as v2.

static const struct of_device_id adc128_of_match[] = {
+	{ .compatible = "ti,adc082s021", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
+	{ .compatible = "ti,adc082s051", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
}

static const struct spi_device_id adc128_id[] = {
+	{ "adc082s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
+	{ "adc082s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
}

Currently it uses spi_get_device_match_data() to extract config.

And in v3, I will use enum while setting up config.

+static const struct adc128_configuration adc128_config[] = {
+       [ADC128_CONFIG_INDEX_082S] = {
+               .channels = adc082s021_channels,
+               .num_channels = ARRAY_SIZE(adc082s021_channels)
}

> > 
> > static const struct of_device_id adc128_of_match[] = {
> > 	{ .compatible = "ti,adc082s021", },
> > }
> > 
> > > Or I think you can make it irrelevant by not using an array at all.
> > > static const struct ad128_configruation adc082s021_config = {
> > > };
> > > 
> > > etc then just use the address of the right one directly.
> > > 
> > > In this driver, I suspect that is simpler than using the array.
> > >   
> > > > +enum adc128_configuration_index {
> > > > +	ADC128_CONFIG_INDEX_082S,
> > > > +	ADC128_CONFIG_INDEX_102S,
> > > > +	ADC128_CONFIG_INDEX_122S,
> > > > +	ADC128_CONFIG_INDEX_124S,
> > > > +	ADC128_CONFIG_INDEX_128S,  
> > >   
> > > >  };
> > > >  
> > > >  static const struct iio_info adc128_info = {
> > > > @@ -177,31 +226,43 @@ static int adc128_probe(struct spi_device *spi)
> > > >  }
> > > >  
> > > >  static const struct of_device_id adc128_of_match[] = {
> > > > -	{ .compatible = "ti,adc128s052", .data = &adc128_config[0] },
> > > > -	{ .compatible = "ti,adc122s021", .data = &adc128_config[1] },
> > > > -	{ .compatible = "ti,adc122s051", .data = &adc128_config[1] },
> > > > -	{ .compatible = "ti,adc122s101", .data = &adc128_config[1] },
> > > > -	{ .compatible = "ti,adc124s021", .data = &adc128_config[2] },
> > > > -	{ .compatible = "ti,adc124s051", .data = &adc128_config[2] },
> > > > -	{ .compatible = "ti,adc124s101", .data = &adc128_config[2] },
> > > > +	{ .compatible = "ti,adc082s021", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
> > > > +	{ .compatible = "ti,adc082s051", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
> > > > +	{ .compatible = "ti,adc082s101", .data = &adc128_config[ADC128_CONFIG_INDEX_082S] },
> > > > +	{ .compatible = "ti,adc102s021", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
> > > > +	{ .compatible = "ti,adc102s051", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
> > > > +	{ .compatible = "ti,adc102s101", .data = &adc128_config[ADC128_CONFIG_INDEX_102S] },
> > > > +	{ .compatible = "ti,adc122s021", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
> > > > +	{ .compatible = "ti,adc122s051", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
> > > > +	{ .compatible = "ti,adc122s101", .data = &adc128_config[ADC128_CONFIG_INDEX_122S] },
> > > > +	{ .compatible = "ti,adc124s021", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
> > > > +	{ .compatible = "ti,adc124s051", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
> > > > +	{ .compatible = "ti,adc124s101", .data = &adc128_config[ADC128_CONFIG_INDEX_124S] },
> > > > +	{ .compatible = "ti,adc128s052", .data = &adc128_config[ADC128_CONFIG_INDEX_128S] },
> > > >  	{ /* sentinel */ },
> > > >  };
> > > >  MODULE_DEVICE_TABLE(of, adc128_of_match);
> > > >  
> > > >  static const struct spi_device_id adc128_id[] = {
> > > > -	{ "adc128s052", (kernel_ulong_t)&adc128_config[0] },
> > > > -	{ "adc122s021",	(kernel_ulong_t)&adc128_config[1] },
> > > > -	{ "adc122s051",	(kernel_ulong_t)&adc128_config[1] },
> > > > -	{ "adc122s101",	(kernel_ulong_t)&adc128_config[1] },
> > > > -	{ "adc124s021", (kernel_ulong_t)&adc128_config[2] },
> > > > -	{ "adc124s051", (kernel_ulong_t)&adc128_config[2] },
> > > > -	{ "adc124s101", (kernel_ulong_t)&adc128_config[2] },
> > > > +	{ "adc082s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
> > > > +	{ "adc082s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
> > > > +	{ "adc082s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_082S] },
> > > > +	{ "adc102s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
> > > > +	{ "adc102s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
> > > > +	{ "adc102s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_102S] },
> > > > +	{ "adc122s021",	(kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
> > > > +	{ "adc122s051",	(kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
> > > > +	{ "adc122s101",	(kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_122S] },
> > > > +	{ "adc124s021", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> > > > +	{ "adc124s051", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> > > > +	{ "adc124s101", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> > > > +	{ "adc128s052", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_128S] },
> > > >  	{ }
> > > >  };
> > > >  MODULE_DEVICE_TABLE(spi, adc128_id);
> > > >  
> > > >  static const struct acpi_device_id adc128_acpi_match[] = {
> > > > -	{ "AANT1280", (kernel_ulong_t)&adc128_config[2] },
> > > > +	{ "AANT1280", (kernel_ulong_t)&adc128_config[ADC128_CONFIG_INDEX_124S] },
> > > >  	{ }
> > > >  };
> > > >  MODULE_DEVICE_TABLE(acpi, adc128_acpi_match);  
> > >   
> > 
>