linux-kernel - [PATCH] [PATCH v1] spi: cadence: Add usleep_range() for cdns_spi_fill_tx

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Date:   Mon, 16 Apr 2018 14:46:40 +0800
From:   sxauwsk <sxauwsk@....com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        wangshikai@...o-instrument.cn, sxauwsk <sxauwsk@....com>,
        guojian <guojian@...oinstrument.net>
Subject: [PATCH] [PATCH v1] spi: cadence: Add usleep_range() for  cdns_spi_fill_tx_fifo()

In case of xspi work in busy condition, may send bytes failed.
once something wrong, spi controller did't work any more

My test found this situation appear in both of read/write process.
so when TX FIFO is full, add one byte delay before send data;

Signed-off-by: sxauwsk <sxauwsk@....com>
Signed-off-by: guojian <guojian@...oinstrument.net>
Signed-off-by: wangshikai <wangshikai@...o-instrument.cn>
---
 drivers/spi/spi-cadence.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index 66ae055..9694042 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -315,9 +315,11 @@ static void cdns_spi_fill_tx_fifo(struct cdns_spi *xspi)
 	       (xspi->tx_bytes > 0)) {
 
 		/* When xspi in busy condition, bytes may send failed,
-		 * caused communication failure so add one byte delay
+		 * then spi control did't work thoroughly, add one byte delay
 		 */
-		usleep_range(10, 20);
+		if (cdns_spi_read(xspi, CDNS_SPI_ISR_OFFSET) &
+		    CDNS_SPI_IXR_TXFULL_MASK)
+			usleep_range(10, 20);
 
 		if (xspi->txbuf)
 			cdns_spi_write(xspi, CDNS_SPI_TXD, *xspi->txbuf++);
-- 
1.7.9.5