[PATCH 2/3] spi: fsl-dspi: fix logic bug introduced by previous commit

[Vladimir Oltean]

dspi_rxtx() is actually "rx, and then tx if necessary". Refactoring the
code to look at dspi->len outside of this function means we are losing a
necessary call to dspi_fifo_read(). This makes XSPI-based transfers
eventually hang.

I don't necessarily agree with the premise that using an errno value
privately within the driver is an anti-pattern, but let's at least make
the code functionally correct and use a boolean to track whether there
is data left to send, while still allowing data to be received.

Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
---
 drivers/spi/spi-fsl-dspi.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index c0a6c6c6459e..e74ff6e9cb02 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -986,15 +986,20 @@ static void dspi_fifo_write(struct fsl_dspi *dspi)
 				dspi->progress, !dspi->irq);
 }
 
-static void dspi_rxtx(struct fsl_dspi *dspi)
+/* Returns false if the buffer to be transmitted is empty, and true if
+ * there is still data to transmit.
+ */
+static bool dspi_rxtx(struct fsl_dspi *dspi)
 {
 	dspi_fifo_read(dspi);
 
 	if (!dspi->len)
 		/* Success! */
-		return;
+		return false;
 
 	dspi_fifo_write(dspi);
+
+	return true;
 }
 
 static int dspi_poll(struct fsl_dspi *dspi)
@@ -1003,7 +1008,7 @@ static int dspi_poll(struct fsl_dspi *dspi)
 	int err = 0;
 	u32 spi_sr;
 
-	while (dspi->len) {
+	do {
 		for (tries = 1000; tries > 0; --tries) {
 			regmap_read(dspi->regmap, SPI_SR, &spi_sr);
 			regmap_write(dspi->regmap, SPI_SR, spi_sr);
@@ -1014,8 +1019,7 @@ static int dspi_poll(struct fsl_dspi *dspi)
 			err = -ETIMEDOUT;
 			break;
 		}
-		dspi_rxtx(dspi);
-	}
+	} while (dspi_rxtx(dspi));
 
 	return err;
 }
@@ -1031,9 +1035,7 @@ static irqreturn_t dspi_interrupt(int irq, void *dev_id)
 	if (!(spi_sr & SPI_SR_CMDTCF))
 		return IRQ_NONE;
 
-	dspi_rxtx(dspi);
-
-	if (!dspi->len)
+	if (dspi_rxtx(dspi) == false)
 		complete(&dspi->xfer_done);
 
 	return IRQ_HANDLED;
-- 
2.34.1


--zwdlutain6qm4enm
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="0003-spi-fsl-dspi-Store-status-directly-in-cur_msg-status.patch"