spi: cadence: Add usleep_range() for cdns_spi_fill_tx_fifo()

BugLink: http://bugs.launchpad.net/bugs/1794889
[ Upstream commit 49530e6411789c1b9ea3ebc58e520c19d1c3752f ]

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@163.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index 5c9516ae4942e5cf8b2ef381d2ecd496803cbf14..4a001634023e09b8e83b8e6b82b5af557e2c0853 100644 (file)
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -313,6 +313,14 @@ static void cdns_spi_fill_tx_fifo(struct cdns_spi *xspi)
 
        while ((trans_cnt < CDNS_SPI_FIFO_DEPTH) &&
               (xspi->tx_bytes > 0)) {
+
+               /* When xspi in busy condition, bytes may send failed,
+                * then spi control did't work thoroughly, add one byte delay
+                */
+               if (cdns_spi_read(xspi, CDNS_SPI_ISR) &
+                   CDNS_SPI_IXR_TXFULL)
+                       usleep_range(10, 20);
+
                if (xspi->txbuf)
                        cdns_spi_write(xspi, CDNS_SPI_TXD, *xspi->txbuf++);
                else