[PATCH v5 09/12] iio: dac: ad5686: implement new sync() op for the spi bus

[Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@kernel.org>]

From: Rodrigo Alencar <rodrigo.alencar@analog.com>

Use of local SPI bus data to manage a collection of SPI transfers and
flush them to the SPI platform driver with the sync() operation. This
allows for faster handling of multiple channel DAC writes, avoiding kernel
overhead per spi_sync() call, which will be helpful when enabling
triggered buffer support.

Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>
---
 drivers/iio/dac/ad5686-spi.c | 125 ++++++++++++++++++++++++++++++++-----------
 drivers/iio/dac/ad5686.c     |   4 +-
 drivers/iio/dac/ad5686.h     |   8 ++-
 drivers/iio/dac/ad5696-i2c.c |   2 +-
 4 files changed, 104 insertions(+), 35 deletions(-)

diff --git a/drivers/iio/dac/ad5686-spi.c b/drivers/iio/dac/ad5686-spi.c
index 6b6ef1d7071f..4a9a365b63bc 100644
--- a/drivers/iio/dac/ad5686-spi.c
+++ b/drivers/iio/dac/ad5686-spi.c
@@ -12,59 +12,91 @@
 #include <linux/errno.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
+#include <linux/overflow.h>
 #include <linux/spi/spi.h>
 
 #include <asm/byteorder.h>
 
 #include "ad5686.h"
 
+/**
+ * struct ad5686_spi_data - SPI bus specific data
+ * @msg: SPI message used for transfers
+ * @size: number of transfers currently in the message
+ * @capacity: maximum number of transfers that can be added to the message
+ * @xfers: array of SPI transfers, allocated with the provided capacity
+ */
+struct ad5686_spi_data {
+	struct spi_message msg;
+	unsigned int size;
+	unsigned int capacity;
+	struct spi_transfer xfers[] __counted_by(capacity);
+};
+
 static int ad5686_spi_write(struct ad5686_state *st,
 			    u8 cmd, u8 addr, u16 val)
 {
-	struct spi_device *spi = to_spi_device(st->dev);
-	u8 tx_len, *buf;
+	struct ad5686_spi_data *bus_data = st->bus_data;
+	struct spi_transfer *xfer;
 
+	if (bus_data->size >= bus_data->capacity)
+		return -E2BIG;
+
+	if (bus_data->size)
+		bus_data->xfers[bus_data->size - 1].cs_change = 1;
+	else
+		spi_message_init(&bus_data->msg);
+
+	xfer = &bus_data->xfers[bus_data->size];
 	switch (st->chip_info->regmap_type) {
 	case AD5310_REGMAP:
-		st->data[0].d16 = cpu_to_be16(AD5310_CMD(cmd) |
-					      val);
-		buf = &st->data[0].d8[0];
-		tx_len = 2;
+		st->data[bus_data->size].d16 =
+			cpu_to_be16(AD5310_CMD(cmd) | val);
+		*xfer = (struct spi_transfer) {
+			.tx_buf = &st->data[bus_data->size].d16,
+			.len = sizeof(st->data[bus_data->size].d16),
+		};
 		break;
 	case AD5683_REGMAP:
-		st->data[0].d32 = cpu_to_be32(AD5686_CMD(cmd) |
-					      AD5683_DATA(val));
-		buf = &st->data[0].d8[1];
-		tx_len = 3;
+		st->data[bus_data->size].d32 =
+			cpu_to_be32(AD5686_CMD(cmd) | AD5683_DATA(val));
+		*xfer = (struct spi_transfer) {
+			.tx_buf = &st->data[bus_data->size].d8[1],
+			.len = sizeof(st->data[bus_data->size].d8) - 1,
+		};
 		break;
 	case AD5686_REGMAP:
-		st->data[0].d32 = cpu_to_be32(AD5686_CMD(cmd) |
-					      AD5686_ADDR(addr) |
-					      val);
-		buf = &st->data[0].d8[1];
-		tx_len = 3;
+		st->data[bus_data->size].d32 =
+			cpu_to_be32(AD5686_CMD(cmd) | AD5686_ADDR(addr) | val);
+		*xfer = (struct spi_transfer) {
+			.tx_buf = &st->data[bus_data->size].d8[1],
+			.len = sizeof(st->data[bus_data->size].d8) - 1,
+		};
 		break;
 	default:
 		return -EINVAL;
 	}
 
-	return spi_write(spi, buf, tx_len);
+	spi_message_add_tail(xfer, &bus_data->msg);
+	bus_data->size++;
+
+	return 0;
+}
+
+static int ad5686_spi_sync(struct ad5686_state *st)
+{
+	struct spi_device *spi = to_spi_device(st->dev);
+	struct ad5686_spi_data *bus_data = st->bus_data;
+
+	bus_data->size = 0; /* always reset, even on sync failure */
+	return spi_sync(spi, &bus_data->msg);
 }
 
 static int ad5686_spi_read(struct ad5686_state *st, u8 addr)
 {
-	struct spi_transfer t[] = {
-		{
-			.tx_buf = &st->data[0].d8[1],
-			.len = 3,
-			.cs_change = 1,
-		}, {
-			.tx_buf = &st->data[1].d8[1],
-			.rx_buf = &st->data[2].d8[1],
-			.len = 3,
-		},
-	};
 	struct spi_device *spi = to_spi_device(st->dev);
+	struct ad5686_spi_data *bus_data = st->bus_data;
+	struct spi_transfer *xfer = &bus_data->xfers[0];
 	u8 cmd = 0;
 	int ret;
 
@@ -85,8 +117,21 @@ static int ad5686_spi_read(struct ad5686_state *st, u8 addr)
 				      AD5686_ADDR(addr));
 	st->data[1].d32 = cpu_to_be32(AD5686_CMD(AD5686_CMD_NOOP));
 
-	ret = spi_sync_transfer(spi, t, ARRAY_SIZE(t));
-	if (ret < 0)
+	xfer[0] = (struct spi_transfer) {
+		.tx_buf = &st->data[0].d8[1],
+		.len = sizeof(st->data[0].d8) - 1,
+		.cs_change = 1,
+	};
+	xfer[1] = (struct spi_transfer) {
+		.tx_buf = &st->data[1].d8[1],
+		.rx_buf = &st->data[2].d8[1],
+		.len = sizeof(st->data[1].d8) - 1,
+	};
+
+	spi_message_init_with_transfers(&bus_data->msg, xfer, 2);
+
+	ret = spi_sync(spi, &bus_data->msg);
+	if (ret)
 		return ret;
 
 	return be32_to_cpu(st->data[2].d32);
@@ -95,12 +140,30 @@ static int ad5686_spi_read(struct ad5686_state *st, u8 addr)
 static const struct ad5686_bus_ops ad5686_spi_ops = {
 	.write = ad5686_spi_write,
 	.read = ad5686_spi_read,
+	.sync = ad5686_spi_sync,
 };
 
 static int ad5686_spi_probe(struct spi_device *spi)
 {
-	return ad5686_probe(&spi->dev, spi_get_device_match_data(spi),
-			    spi->modalias, &ad5686_spi_ops);
+	const struct ad5686_chip_info *info;
+	struct ad5686_spi_data *bus_data;
+	struct device *dev = &spi->dev;
+	unsigned int capacity;
+
+	info = spi_get_device_match_data(spi);
+	if (!info)
+		return -ENODEV;
+
+	/* read operation requires at least 2 transfers */
+	capacity = max(info->num_channels, 2);
+	bus_data = devm_kzalloc(dev, struct_size(bus_data, xfers, capacity),
+				GFP_KERNEL);
+	if (!bus_data)
+		return -ENOMEM;
+
+	bus_data->capacity = capacity;
+
+	return ad5686_probe(dev, info, spi->modalias, &ad5686_spi_ops, bus_data);
 }
 
 static const struct spi_device_id ad5686_spi_id[] = {
diff --git a/drivers/iio/dac/ad5686.c b/drivers/iio/dac/ad5686.c
index 713fe71ad1e7..75dd7921c67b 100644
--- a/drivers/iio/dac/ad5686.c
+++ b/drivers/iio/dac/ad5686.c
@@ -472,7 +472,8 @@ EXPORT_SYMBOL_NS_GPL(ad5679r_chip_info, "IIO_AD5686");
 
 int ad5686_probe(struct device *dev,
 		 const struct ad5686_chip_info *chip_info,
-		 const char *name, const struct ad5686_bus_ops *ops)
+		 const char *name, const struct ad5686_bus_ops *ops,
+		 void *bus_data)
 {
 	struct reset_control *rstc;
 	struct ad5686_state *st;
@@ -487,6 +488,7 @@ int ad5686_probe(struct device *dev,
 
 	st->dev = dev;
 	st->ops = ops;
+	st->bus_data = bus_data;
 	st->chip_info = chip_info;
 
 	rstc = devm_reset_control_get_optional_exclusive(dev, NULL);
diff --git a/drivers/iio/dac/ad5686.h b/drivers/iio/dac/ad5686.h
index 9a192b0a2d7a..cb884334e94a 100644
--- a/drivers/iio/dac/ad5686.h
+++ b/drivers/iio/dac/ad5686.h
@@ -23,6 +23,7 @@
 
 #define AD5686_ADDR_DAC(chan)			(0x1 << (chan))
 #define AD5686_ADDR_ALL_DAC			0xF
+#define AD5686_MAX_CHANNELS			16
 
 #define AD5686_CMD_NOOP				0x0
 #define AD5686_CMD_WRITE_INPUT_N		0x1
@@ -130,6 +131,7 @@ extern const struct ad5686_chip_info ad5679r_chip_info;
  * @use_internal_vref:	set to true if the internal reference voltage is used
  * @lock:		lock to protect access to state fields, which includes
  *			the data buffer during regmap ops
+ * @bus_data:		bus specific data
  * @data:		transfer buffers
  */
 struct ad5686_state {
@@ -142,6 +144,7 @@ struct ad5686_state {
 	unsigned int			pwr_down_mode;
 	bool				use_internal_vref;
 	struct mutex			lock;
+	void				*bus_data;
 
 	/*
 	 * DMA (thus cache coherency maintenance) may require the
@@ -152,13 +155,14 @@ struct ad5686_state {
 		__be32 d32;
 		__be16 d16;
 		u8 d8[4];
-	} data[3] __aligned(IIO_DMA_MINALIGN);
+	} data[AD5686_MAX_CHANNELS] __aligned(IIO_DMA_MINALIGN);
 };
 
 
 int ad5686_probe(struct device *dev,
 		 const struct ad5686_chip_info *chip_info,
-		 const char *name, const struct ad5686_bus_ops *ops);
+		 const char *name, const struct ad5686_bus_ops *ops,
+		 void *bus_data);
 
 static inline int ad5686_write(struct ad5686_state *st, u8 cmd, u8 addr, u16 val)
 {
diff --git a/drivers/iio/dac/ad5696-i2c.c b/drivers/iio/dac/ad5696-i2c.c
index 279309329b64..28c97ded43ce 100644
--- a/drivers/iio/dac/ad5696-i2c.c
+++ b/drivers/iio/dac/ad5696-i2c.c
@@ -70,7 +70,7 @@ static const struct ad5686_bus_ops ad5686_i2c_ops = {
 static int ad5686_i2c_probe(struct i2c_client *i2c)
 {
 	return ad5686_probe(&i2c->dev, i2c_get_match_data(i2c),
-			    i2c->name, &ad5686_i2c_ops);
+			    i2c->name, &ad5686_i2c_ops, NULL);
 }
 
 static const struct i2c_device_id ad5686_i2c_id[] = {

-- 
2.43.0