linux-kernel - [PATCH] spi: lpspi: fix dataloss when SS is inactivated between every words

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Date:   Thu, 21 Mar 2019 09:57:12 +0000
From:   Clark Wang <xiaoning.wang@....com>
To:     "broonie@...nel.org" <broonie@...nel.org>
CC:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] spi: lpspi: fix dataloss when SS is inactivated between every
 words

If we don't use CONT to keep SS activated or use DMA mode without
cs-gpio, SS will be inactivated between every words. The word here
means the data sent once which length can be set as 1/2/4 bytes.

In the isr function, we read the FSR_RXCOUNT just behind the
fsl_lpspi_read_rx_fifo. This causes the value of FSR_RXCOUNT cannot
reflect whether there is still data not sent timely. So do this
judgement by FSR_TXCOUNT.

Signed-off-by: Clark Wang <xiaoning.wang@....com>
---
 drivers/spi/spi-fsl-lpspi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
index 4de8eb378752..0252cae0b35b 100644
--- a/drivers/spi/spi-fsl-lpspi.c
+++ b/drivers/spi/spi-fsl-lpspi.c
@@ -77,7 +77,7 @@
 #define CFGR1_PCSPOL	BIT(8)
 #define CFGR1_NOSTALL	BIT(3)
 #define CFGR1_MASTER	BIT(0)
-#define FSR_RXCOUNT	(BIT(16)|BIT(17)|BIT(18))
+#define FSR_TXCOUNT	(0xFF)
 #define RSR_RXEMPTY	BIT(1)
 #define TCR_CPOL	BIT(31)
 #define TCR_CPHA	BIT(30)
@@ -765,7 +765,7 @@ static irqreturn_t fsl_lpspi_isr(int irq, void *dev_id)
 	}
 
 	if (temp_SR & SR_MBF ||
-	    readl(fsl_lpspi->base + IMX7ULP_FSR) & FSR_RXCOUNT) {
+	    readl(fsl_lpspi->base + IMX7ULP_FSR) & FSR_TXCOUNT) {
 		writel(SR_FCF, fsl_lpspi->base + IMX7ULP_SR);
 		fsl_lpspi_intctrl(fsl_lpspi, IER_FCIE);
 		return IRQ_HANDLED;
-- 
2.17.1