2020-05-28 15:30:36

by Tim Harvey

Subject: [PATCH] can: mcp251x: add support for half duplex controllers

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 <[email protected]>
---
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

2020-06-30 18:52:07

by Tim Harvey

Subject: Re: [PATCH] can: mcp251x: add support for half duplex controllers

On Thu, May 28, 2020 at 8:28 AM Tim Harvey <[email protected]> wrote:
>
> 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 <[email protected]>
> ---
> 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
>

Marc / Wolfgang,

Any feedback on this?

Best Regards,

Tim