iio:imu:adis: Add paging support

Some of the newer generation devices from the ADIS16XXX series have more
registers than what can be supported with the current register addressing
scheme. These devices implement register paging to support a larger register
range. Each page is 128 registers large and the currently active page can be
selected via register 0x00 in each page. This patch implements transparent
paging inside the common adis library. The register read/write interface stays
the same and when a register is accessed the library automatically switches to
the correct page if it is not already selected. The page number is encoded in
the upper bits of the register number, e.g. register 0x5 of page 1 is 0x85.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/imu/adis.c

@@ -30,6 +30,7 @@
 int adis_write_reg(struct adis *adis, unsigned int reg,
 	unsigned int value, unsigned int size)
 {
+	unsigned int page = reg / ADIS_PAGE_SIZE;
 	int ret, i;
 	struct spi_message msg;
 	struct spi_transfer xfers[] = {
@@ -56,39 +57,53 @@ int adis_write_reg(struct adis *adis, unsigned int reg,
 			.bits_per_word = 8,
 			.len = 2,
 			.delay_usecs = adis->data->write_delay,
+		}, {
+			.tx_buf = adis->tx + 8,
+			.bits_per_word = 8,
+			.len = 2,
+			.delay_usecs = adis->data->write_delay,
 		},
 	};
 
 	mutex_lock(&adis->txrx_lock);
 
 	spi_message_init(&msg);
+
+	if (adis->current_page != page) {
+		adis->tx[0] = ADIS_WRITE_REG(ADIS_REG_PAGE_ID);
+		adis->tx[1] = page;
+		spi_message_add_tail(&xfers[0], &msg);
+	}
+
 	switch (size) {
 	case 4:
-		adis->tx[6] = ADIS_WRITE_REG(reg + 3);
-		adis->tx[7] = (value >> 24) & 0xff;
-		adis->tx[4] = ADIS_WRITE_REG(reg + 2);
-		adis->tx[5] = (value >> 16) & 0xff;
+		adis->tx[8] = ADIS_WRITE_REG(reg + 3);
+		adis->tx[9] = (value >> 24) & 0xff;
+		adis->tx[6] = ADIS_WRITE_REG(reg + 2);
+		adis->tx[7] = (value >> 16) & 0xff;
 	case 2:
-		adis->tx[2] = ADIS_WRITE_REG(reg + 1);
-		adis->tx[3] = (value >> 8) & 0xff;
+		adis->tx[4] = ADIS_WRITE_REG(reg + 1);
+		adis->tx[5] = (value >> 8) & 0xff;
 	case 1:
-		adis->tx[0] = ADIS_WRITE_REG(reg);
-		adis->tx[1] = value & 0xff;
+		adis->tx[2] = ADIS_WRITE_REG(reg);
+		adis->tx[3] = value & 0xff;
 		break;
 	default:
 		ret = -EINVAL;
 		goto out_unlock;
 	}
 
-	xfers[size - 1].cs_change = 0;
+	xfers[size].cs_change = 0;
 
-	for (i = 0; i < size; i++)
+	for (i = 1; i <= size; i++)
 		spi_message_add_tail(&xfers[i], &msg);
 
 	ret = spi_sync(adis->spi, &msg);
 	if (ret) {
 		dev_err(&adis->spi->dev, "Failed to write register 0x%02X: %d\n",
 				reg, ret);
+	} else {
+		adis->current_page = page;
 	}
 
 out_unlock:
@@ -107,6 +122,7 @@ EXPORT_SYMBOL_GPL(adis_write_reg);
 int adis_read_reg(struct adis *adis, unsigned int reg,
 	unsigned int *val, unsigned int size)
 {
+	unsigned int page = reg / ADIS_PAGE_SIZE;
 	struct spi_message msg;
 	int ret;
 	struct spi_transfer xfers[] = {
@@ -115,9 +131,15 @@ int adis_read_reg(struct adis *adis, unsigned int reg,
 			.bits_per_word = 8,
 			.len = 2,
 			.cs_change = 1,
-			.delay_usecs = adis->data->read_delay,
+			.delay_usecs = adis->data->write_delay,
 		}, {
 			.tx_buf = adis->tx + 2,
+			.bits_per_word = 8,
+			.len = 2,
+			.cs_change = 1,
+			.delay_usecs = adis->data->read_delay,
+		}, {
+			.tx_buf = adis->tx + 4,
 			.rx_buf = adis->rx,
 			.bits_per_word = 8,
 			.len = 2,
@@ -134,16 +156,22 @@ int adis_read_reg(struct adis *adis, unsigned int reg,
 	mutex_lock(&adis->txrx_lock);
 	spi_message_init(&msg);
 
+	if (adis->current_page != page) {
+		adis->tx[0] = ADIS_WRITE_REG(ADIS_REG_PAGE_ID);
+		adis->tx[1] = page;
+		spi_message_add_tail(&xfers[0], &msg);
+	}
+
 	switch (size) {
 	case 4:
-		adis->tx[0] = ADIS_READ_REG(reg + 2);
-		adis->tx[1] = 0;
-		spi_message_add_tail(&xfers[0], &msg);
-	case 2:
-		adis->tx[2] = ADIS_READ_REG(reg);
+		adis->tx[2] = ADIS_READ_REG(reg + 2);
 		adis->tx[3] = 0;
 		spi_message_add_tail(&xfers[1], &msg);
+	case 2:
+		adis->tx[4] = ADIS_READ_REG(reg);
+		adis->tx[5] = 0;
 		spi_message_add_tail(&xfers[2], &msg);
+		spi_message_add_tail(&xfers[3], &msg);
 		break;
 	default:
 		ret = -EINVAL;
@@ -155,6 +183,8 @@ int adis_read_reg(struct adis *adis, unsigned int reg,
 		dev_err(&adis->spi->dev, "Failed to read register 0x%02X: %d\n",
 				reg, ret);
 		goto out_unlock;
+	} else {
+		adis->current_page = page;
 	}
 
 	switch (size) {
@@ -390,6 +420,14 @@ int adis_init(struct adis *adis, struct iio_dev *indio_dev,
 	adis->data = data;
 	iio_device_set_drvdata(indio_dev, adis);
 
+	if (data->has_paging) {
+		/* Need to set the page before first read/write */
+		adis->current_page = -1;
+	} else {
+		/* Page will always be 0 */
+		adis->current_page = 0;
+	}
+
 	return adis_enable_irq(adis, false);
 }
 EXPORT_SYMBOL_GPL(adis_init);

drivers/iio/imu/adis_buffer.c

@@ -83,10 +83,25 @@ static irqreturn_t adis_trigger_handler(int irq, void *p)
 	if (!adis->buffer)
 		return -ENOMEM;
 
+	if (adis->data->has_paging) {
+		mutex_lock(&adis->txrx_lock);
+		if (adis->current_page != 0) {
+			adis->tx[0] = ADIS_WRITE_REG(ADIS_REG_PAGE_ID);
+			adis->tx[1] = 0;
+			spi_write(adis->spi, adis->tx, 2);
+		}
+	}
+
 	ret = spi_sync(adis->spi, &adis->msg);
 	if (ret)
 		dev_err(&adis->spi->dev, "Failed to read data: %d", ret);
 
+
+	if (adis->data->has_paging) {
+		adis->current_page = 0;
+		mutex_unlock(&adis->txrx_lock);
+	}
+
 	/* Guaranteed to be aligned with 8 byte boundary */
 	if (indio_dev->scan_timestamp) {
 		void *b = adis->buffer + indio_dev->scan_bytes - sizeof(s64);

include/linux/iio/imu/adis.h

@@ -14,8 +14,11 @@
 #include <linux/interrupt.h>
 #include <linux/iio/types.h>
 
-#define ADIS_WRITE_REG(reg) (0x80 | (reg))
-#define ADIS_READ_REG(reg) (reg)
+#define ADIS_WRITE_REG(reg) ((0x80 | (reg)))
+#define ADIS_READ_REG(reg) ((reg) & 0x7f)
+
+#define ADIS_PAGE_SIZE 0x80
+#define ADIS_REG_PAGE_ID 0x00
 
 /**
  * struct adis_data - ADIS chip variant specific data
@@ -40,6 +43,8 @@ struct adis_data {
 
 	const char * const *status_error_msgs;
 	unsigned int status_error_mask;
+
+	bool has_paging;
 };
 
 struct adis {
@@ -51,6 +56,7 @@ struct adis {
 	struct mutex		txrx_lock;
 	struct spi_message	msg;
 	struct spi_transfer	*xfer;
+	unsigned int		current_page;
 	void			*buffer;
 
 	uint8_t			tx[10] ____cacheline_aligned;