[PATCH] spi: davinci: Drop the preload of TX buffer before read/writes operations

[Bastien Curutchet]

A write to the TX buffer is performed before entering the loop to "avoid
clock starvation". This sometimes results in subsequent writes in
davinci_spi_xfer_data() to occur while the TXFULL bit is asserted,
leading to write failures.

Remove the preload of the TX buffer.

Signed-off-by: Bastien Curutchet <bastien.curutchet at bootlin.com>
---
Hi all,

I've ran into write failures to flash on my platform based on the
DAVINCI/OMAP L138. This patch fixes it.

 drivers/spi/davinci_spi.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c
index 25f5e9fdeb..07c46b8b66 100644
--- a/drivers/spi/davinci_spi.c
+++ b/drivers/spi/davinci_spi.c
@@ -129,9 +129,6 @@ static int davinci_spi_read(struct davinci_spi_slave *ds, unsigned int len,
 	while (readl(&ds->regs->buf) & SPIBUF_TXFULL_MASK)
 		;
 
-	/* preload the TX buffer to avoid clock starvation */
-	writel(data1_reg_val, &ds->regs->dat1);
-
 	/* keep reading 1 byte until only 1 byte left */
 	while ((len--) > 1)
 		*rxp++ = davinci_spi_xfer_data(ds, data1_reg_val);
@@ -159,12 +156,6 @@ static int davinci_spi_write(struct davinci_spi_slave *ds, unsigned int len,
 	while (readl(&ds->regs->buf) & SPIBUF_TXFULL_MASK)
 		;
 
-	/* preload the TX buffer to avoid clock starvation */
-	if (len > 2) {
-		writel(data1_reg_val | *txp++, &ds->regs->dat1);
-		len--;
-	}
-
 	/* keep writing 1 byte until only 1 byte left */
 	while ((len--) > 1)
 		davinci_spi_xfer_data(ds, data1_reg_val | *txp++);
-- 
2.46.0