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Subject[PATCH] can: mcp251x: add support for half duplex controllers
Date
Some SPI host controllers do not support full-duplex SPI and are
marked as such via the SPI_CONTROLLER_HALF_DUPLEX controller flag.

For such controllers use half duplex transactions but retain full
duplex transactions for the controllers that can handle those.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
---
drivers/net/can/spi/mcp251x.c | 34 +++++++++++++++++++++++++++-------
1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c
index 5009ff2..203ef20 100644
--- a/drivers/net/can/spi/mcp251x.c
+++ b/drivers/net/can/spi/mcp251x.c
@@ -290,8 +290,12 @@ static u8 mcp251x_read_reg(struct spi_device *spi, u8 reg)
priv->spi_tx_buf[0] = INSTRUCTION_READ;
priv->spi_tx_buf[1] = reg;

- mcp251x_spi_trans(spi, 3);
- val = priv->spi_rx_buf[2];
+ if (spi->controller->flags & SPI_CONTROLLER_HALF_DUPLEX) {
+ spi_write_then_read(spi, priv->spi_tx_buf, 2, &val, 1);
+ } else {
+ mcp251x_spi_trans(spi, 3);
+ val = priv->spi_rx_buf[2];
+ }

return val;
}
@@ -303,10 +307,18 @@ static void mcp251x_read_2regs(struct spi_device *spi, u8 reg, u8 *v1, u8 *v2)
priv->spi_tx_buf[0] = INSTRUCTION_READ;
priv->spi_tx_buf[1] = reg;

- mcp251x_spi_trans(spi, 4);
+ if (spi->controller->flags & SPI_CONTROLLER_HALF_DUPLEX) {
+ u8 val[2] = { 0 };

- *v1 = priv->spi_rx_buf[2];
- *v2 = priv->spi_rx_buf[3];
+ spi_write_then_read(spi, priv->spi_tx_buf, 2, val, 2);
+ *v1 = val[0];
+ *v2 = val[1];
+ } else {
+ mcp251x_spi_trans(spi, 4);
+
+ *v1 = priv->spi_rx_buf[2];
+ *v2 = priv->spi_rx_buf[3];
+ }
}

static void mcp251x_write_reg(struct spi_device *spi, u8 reg, u8 val)
@@ -409,8 +421,16 @@ static void mcp251x_hw_rx_frame(struct spi_device *spi, u8 *buf,
buf[i] = mcp251x_read_reg(spi, RXBCTRL(buf_idx) + i);
} else {
priv->spi_tx_buf[RXBCTRL_OFF] = INSTRUCTION_READ_RXB(buf_idx);
- mcp251x_spi_trans(spi, SPI_TRANSFER_BUF_LEN);
- memcpy(buf, priv->spi_rx_buf, SPI_TRANSFER_BUF_LEN);
+ if (spi->controller->flags & SPI_CONTROLLER_HALF_DUPLEX) {
+ spi_write_then_read(spi, priv->spi_tx_buf, 1,
+ priv->spi_rx_buf,
+ SPI_TRANSFER_BUF_LEN);
+ memcpy(buf + 1, priv->spi_rx_buf,
+ SPI_TRANSFER_BUF_LEN - 1);
+ } else {
+ mcp251x_spi_trans(spi, SPI_TRANSFER_BUF_LEN);
+ memcpy(buf, priv->spi_rx_buf, SPI_TRANSFER_BUF_LEN);
+ }
}
}

--
2.7.4
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