iio: adc: ad7380: prepare for parts with more channels

The current driver supports only parts with 2 channels.
In order to prepare the support of new compatible ADCs with more
channels, this commit:
  - defines MAX_NUM_CHANNEL to specify the maximum number of
    channels currently supported by the driver
  - adds available_scan_mask member in ad7380_chip_info structure
  - fixes spi xfer struct len depending on number of channels
  - fixes scan_data.raw buffer size to handle more channels
  - adds a timing specifications structure in ad7380_chip_info structure
Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Link: https://lore.kernel.org/r/20240528-adding-new-ad738x-driver-v7-5-4cd70a4c12c8@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad7380.c

@@ -27,6 +27,7 @@
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
 
+#define MAX_NUM_CHANNELS		2
 /* 2.5V internal reference voltage */
 #define AD7380_INTERNAL_REF_MV		2500
 
@@ -63,12 +64,19 @@
 #define AD7380_ALERT_LOW_TH		GENMASK(11, 0)
 #define AD7380_ALERT_HIGH_TH		GENMASK(11, 0)
 
+#define T_CONVERT_NS 190		/* conversion time */
+struct ad7380_timing_specs {
+	const unsigned int t_csh_ns;	/* CS minimum high time */
+};
+
 struct ad7380_chip_info {
 	const char *name;
 	const struct iio_chan_spec *channels;
 	unsigned int num_channels;
 	const char * const *vcm_supplies;
 	unsigned int num_vcm_supplies;
+	const unsigned long *available_scan_masks;
+	const struct ad7380_timing_specs *timing_specs;
 };
 
 #define AD7380_CHANNEL(index, bits, diff) {			\
@@ -113,16 +121,24 @@ static const unsigned long ad7380_2_channel_scan_masks[] = {
 	0
 };
 
+static const struct ad7380_timing_specs ad7380_timing = {
+	.t_csh_ns = 10,
+};
+
 static const struct ad7380_chip_info ad7380_chip_info = {
 	.name = "ad7380",
 	.channels = ad7380_channels,
 	.num_channels = ARRAY_SIZE(ad7380_channels),
+	.available_scan_masks = ad7380_2_channel_scan_masks,
+	.timing_specs = &ad7380_timing,
 };
 
 static const struct ad7380_chip_info ad7381_chip_info = {
 	.name = "ad7381",
 	.channels = ad7381_channels,
 	.num_channels = ARRAY_SIZE(ad7381_channels),
+	.available_scan_masks = ad7380_2_channel_scan_masks,
+	.timing_specs = &ad7380_timing,
 };
 
 static const struct ad7380_chip_info ad7383_chip_info = {
@@ -131,6 +147,8 @@ static const struct ad7380_chip_info ad7383_chip_info = {
 	.num_channels = ARRAY_SIZE(ad7383_channels),
 	.vcm_supplies = ad7380_2_channel_vcm_supplies,
 	.num_vcm_supplies = ARRAY_SIZE(ad7380_2_channel_vcm_supplies),
+	.available_scan_masks = ad7380_2_channel_scan_masks,
+	.timing_specs = &ad7380_timing,
 };
 
 static const struct ad7380_chip_info ad7384_chip_info = {
@@ -139,6 +157,8 @@ static const struct ad7380_chip_info ad7384_chip_info = {
 	.num_channels = ARRAY_SIZE(ad7384_channels),
 	.vcm_supplies = ad7380_2_channel_vcm_supplies,
 	.num_vcm_supplies = ARRAY_SIZE(ad7380_2_channel_vcm_supplies),
+	.available_scan_masks = ad7380_2_channel_scan_masks,
+	.timing_specs = &ad7380_timing,
 };
 
 struct ad7380_state {
@@ -146,15 +166,16 @@ struct ad7380_state {
 	struct spi_device *spi;
 	struct regmap *regmap;
 	unsigned int vref_mv;
-	unsigned int vcm_mv[2];
+	unsigned int vcm_mv[MAX_NUM_CHANNELS];
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
-	 * Make the buffer large enough for 2 16-bit samples and one 64-bit
+	 * Make the buffer large enough for MAX_NUM_CHANNELS 16-bit samples and one 64-bit
 	 * aligned 64 bit timestamp.
+	 * As MAX_NUM_CHANNELS is 2 the layout of the structure is the same for all parts
 	 */
 	struct {
-		u16 raw[2];
+		u16 raw[MAX_NUM_CHANNELS];
 
 		s64 ts __aligned(8);
 	} scan_data __aligned(IIO_DMA_MINALIGN);
@@ -192,7 +213,7 @@ static int ad7380_regmap_reg_read(void *context, unsigned int reg,
 			.tx_buf = &st->tx,
 			.cs_change = 1,
 			.cs_change_delay = {
-				.value = 10, /* t[CSH] */
+				.value = st->chip_info->timing_specs->t_csh_ns,
 				.unit = SPI_DELAY_UNIT_NSECS,
 			},
 		}, {
@@ -247,7 +268,8 @@ static irqreturn_t ad7380_trigger_handler(int irq, void *p)
 	struct ad7380_state *st = iio_priv(indio_dev);
 	struct spi_transfer xfer = {
 		.bits_per_word = st->chip_info->channels[0].scan_type.realbits,
-		.len = 4,
+		.len = (st->chip_info->num_channels - 1) *
+		       BITS_TO_BYTES(st->chip_info->channels->scan_type.storagebits),
 		.rx_buf = st->scan_data.raw,
 	};
 	int ret;
@@ -274,21 +296,22 @@ static int ad7380_read_direct(struct ad7380_state *st,
 			.speed_hz = AD7380_REG_WR_SPEED_HZ,
 			.bits_per_word = chan->scan_type.realbits,
 			.delay = {
-				.value = 190, /* t[CONVERT] */
+				.value = T_CONVERT_NS,
 				.unit = SPI_DELAY_UNIT_NSECS,
 			},
 			.cs_change = 1,
 			.cs_change_delay = {
-				.value = 10, /* t[CSH] */
+				.value = st->chip_info->timing_specs->t_csh_ns,
 				.unit = SPI_DELAY_UNIT_NSECS,
 			},
 		},
-		/* then read both channels */
+		/* then read all channels */
 		{
 			.speed_hz = AD7380_REG_WR_SPEED_HZ,
 			.bits_per_word = chan->scan_type.realbits,
 			.rx_buf = st->scan_data.raw,
-			.len = 4,
+			.len = (st->chip_info->num_channels - 1) *
+			       ((chan->scan_type.storagebits > 16) ? 4 : 2),
 		},
 	};
 	int ret;
@@ -469,7 +492,7 @@ static int ad7380_probe(struct spi_device *spi)
 	indio_dev->name = st->chip_info->name;
 	indio_dev->info = &ad7380_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
-	indio_dev->available_scan_masks = ad7380_2_channel_scan_masks;
+	indio_dev->available_scan_masks = st->chip_info->available_scan_masks;
 
 	ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev,
 					      iio_pollfunc_store_time,