linux-kernel - [PATCH] can: mcp251x: convert to half-duplex SPI

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Date:   Tue, 25 Feb 2020 10:35:34 -0800
From:   Tim Harvey <tharvey@...eworks.com>
To:     linux-kernel@...r.kernel.org, linux-can@...r.kernel.org,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     Timo Schlüßler <schluessler@...use.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Tim Harvey <tharvey@...eworks.com>
Subject: [PATCH] can: mcp251x: convert to half-duplex SPI

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@...eworks.com>
---
 drivers/net/can/spi/mcp251x.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c
index 5009ff2..840c31c 100644
--- a/drivers/net/can/spi/mcp251x.c
+++ b/drivers/net/can/spi/mcp251x.c
@@ -290,23 +290,23 @@ 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];
+	spi_write_then_read(spi, priv->spi_tx_buf, 2, &val, 1);
 
 	return val;
 }
 
 static void mcp251x_read_2regs(struct spi_device *spi, u8 reg, u8 *v1, u8 *v2)
 {
+	u8 val[4] = {0};
 	struct mcp251x_priv *priv = spi_get_drvdata(spi);
 
 	priv->spi_tx_buf[0] = INSTRUCTION_READ;
 	priv->spi_tx_buf[1] = reg;
 
-	mcp251x_spi_trans(spi, 4);
+	spi_write_then_read(spi, priv->spi_tx_buf, 2, val, 2);
 
-	*v1 = priv->spi_rx_buf[2];
-	*v2 = priv->spi_rx_buf[3];
+	*v1 = val[0];
+	*v2 = val[1];
 }
 
 static void mcp251x_write_reg(struct spi_device *spi, u8 reg, u8 val)
-- 
2.7.4