From: Tim Harvey <tharvey@xxxxxxxxxxxxx>
Some SPI host controllers such as the Cavium Thunder do not support
full-duplex SPI. Using half-duplex transfers allows the driver to work
with those host controllers.
Signed-off-by: Tim Harvey <tharvey@xxxxxxxxxxxxx>
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
---
Hello,
what about setting up a proper half duplex transfer like this?
Marc
Changes since v1:
- use spi_sync_transfer instead of spi_write_then_read()
drivers/net/can/spi/mcp251x.c | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)
diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c
index a3897baa359f..26b7e4cb51ed 100644
--- a/drivers/net/can/spi/mcp251x.c
+++ b/drivers/net/can/spi/mcp251x.c
@@ -317,13 +317,26 @@ static int mcp251x_spi_trans(struct spi_device *spi, int len)
static u8 mcp251x_read_reg(struct spi_device *spi, u8 reg)
{
struct mcp251x_priv *priv = spi_get_drvdata(spi);
+ struct spi_transfer xfer[] = {
+ {
+ .tx_buf = priv->spi_tx_buf,
+ .len = 2,
+ }, {
+ .rx_buf = priv->spi_rx_buf,
+ .len = 1,
+ },
+ };
u8 val = 0;
+ int err;
priv->spi_tx_buf[0] = INSTRUCTION_READ;
priv->spi_tx_buf[1] = reg;
- mcp251x_spi_trans(spi, 3);
- val = priv->spi_rx_buf[2];
+ err = spi_sync_transfer(spi, xfer, ARRAY_SIZE(xfer));
+ if (err)
+ dev_err(&spi->dev, "spi transfer failed: ret = %d\n", err);
+
+ val = priv->spi_rx_buf[0];
return val;
}
@@ -331,14 +344,26 @@ static u8 mcp251x_read_reg(struct spi_device *spi, u8 reg)
static void mcp251x_read_2regs(struct spi_device *spi, u8 reg, u8 *v1, u8 *v2)
{
struct mcp251x_priv *priv = spi_get_drvdata(spi);
+ struct spi_transfer xfer[] = {
+ {
+ .tx_buf = priv->spi_tx_buf,
+ .len = 2,
+ }, {
+ .rx_buf = priv->spi_rx_buf,
+ .len = 2,
+ },
+ };
+ int err;
priv->spi_tx_buf[0] = INSTRUCTION_READ;
priv->spi_tx_buf[1] = reg;
- mcp251x_spi_trans(spi, 4);
+ err = spi_sync_transfer(spi, xfer, ARRAY_SIZE(xfer));
+ if (err)
+ dev_err(&spi->dev, "spi transfer failed: ret = %d\n", err);
- *v1 = priv->spi_rx_buf[2];
- *v2 = priv->spi_rx_buf[3];
+ *v1 = priv->spi_rx_buf[0];
+ *v2 = priv->spi_rx_buf[1];
}
static void mcp251x_write_reg(struct spi_device *spi, u8 reg, u8 val)
--
2.25.0
