spi: Add spi_write_then_read

Add support for SPI synchronous write followed by read,
this is common interface call from spi-nor to spi drivers.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Adam Ford <aford173@gmail.com> #da850-evm

2 files changed, 44 insertions, 0 deletions

diff --git a/drivers/spi/spi-uclass.c b/drivers/spi/spi-uclass.c
index 88cb2a1..76c4b53 100644
--- a/drivers/spi/spi-uclass.c
+++ b/drivers/spi/spi-uclass.c
@@ -108,6 +108,30 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 	return dm_spi_xfer(slave->dev, bitlen, dout, din, flags);
 }
 
+int spi_write_then_read(struct spi_slave *slave, const u8 *opcode,
+			size_t n_opcode, const u8 *txbuf, u8 *rxbuf,
+			size_t n_buf)
+{
+	unsigned long flags = SPI_XFER_BEGIN;
+	int ret;
+
+	if (n_buf == 0)
+		flags |= SPI_XFER_END;
+
+	ret = spi_xfer(slave, n_opcode * 8, opcode, NULL, flags);
+	if (ret) {
+		debug("spi: failed to send command (%zu bytes): %d\n",
+		      n_opcode, ret);
+	} else if (n_buf != 0) {
+		ret = spi_xfer(slave, n_buf * 8, txbuf, rxbuf, SPI_XFER_END);
+		if (ret)
+			debug("spi: failed to transfer %zu bytes of data: %d\n",
+			      n_buf, ret);
+	}
+
+	return ret;
+}
+
 #if !CONFIG_IS_ENABLED(OF_PLATDATA)
 static int spi_child_post_bind(struct udevice *dev)
 {
diff --git a/include/spi.h b/include/spi.h
index 3785941..5eec0c4 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -248,6 +248,26 @@ int spi_set_wordlen(struct spi_slave *slave, unsigned int wordlen);
 int  spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 		void *din, unsigned long flags);
 
+/**
+ * spi_write_then_read - SPI synchronous write followed by read
+ *
+ * This performs a half duplex transaction in which the first transaction
+ * is to send the opcode and if the length of buf is non-zero then it start
+ * the second transaction as tx or rx based on the need from respective slave.
+ *
+ * @slave:	The SPI slave device with which opcode/data will be exchanged
+ * @opcode:	opcode used for specific transfer
+ * @n_opcode:	size of opcode, in bytes
+ * @txbuf:	buffer into which data to be written
+ * @rxbuf:	buffer into which data will be read
+ * @n_buf:	size of buf (whether it's [tx|rx]buf), in bytes
+ *
+ * Returns: 0 on success, not 0 on failure
+ */
+int spi_write_then_read(struct spi_slave *slave, const u8 *opcode,
+			size_t n_opcode, const u8 *txbuf, u8 *rxbuf,
+			size_t n_buf);
+
 /* Copy memory mapped data */
 void spi_flash_copy_mmap(void *data, void *offset, size_t len);