4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ricardo Ribalda Delgado <ricardo.riba...@gmail.com>

commit 74346841e6f5df5f7b83d5904435d273c507dba6 upstream.

The ACK of an inexistent IRQ can trigger an spurious IRQ that breaks the
txrx logic. This has been observed on axi_quad_spi:3.2 core.

This patch only ACKs IRQs that have not been Acknowledge jet.

Reported-by: Edward Kigwana <ekigw...@scires.com>
Tested-by: Edward Kigwana <ekigw...@scires.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.riba...@gmail.com>
Signed-off-by: Mark Brown <broo...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/spi/spi-xilinx.c |   16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/drivers/spi/spi-xilinx.c
+++ b/drivers/spi/spi-xilinx.c
@@ -249,19 +249,23 @@ static int xilinx_spi_txrx_bufs(struct s
        xspi->tx_ptr = t->tx_buf;
        xspi->rx_ptr = t->rx_buf;
        remaining_words = t->len / xspi->bytes_per_word;
-       reinit_completion(&xspi->done);
 
        if (xspi->irq >= 0 &&  remaining_words > xspi->buffer_size) {
+               u32 isr;
                use_irq = true;
-               xspi->write_fn(XSPI_INTR_TX_EMPTY,
-                               xspi->regs + XIPIF_V123B_IISR_OFFSET);
-               /* Enable the global IPIF interrupt */
-               xspi->write_fn(XIPIF_V123B_GINTR_ENABLE,
-                               xspi->regs + XIPIF_V123B_DGIER_OFFSET);
                /* Inhibit irq to avoid spurious irqs on tx_empty*/
                cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET);
                xspi->write_fn(cr | XSPI_CR_TRANS_INHIBIT,
                               xspi->regs + XSPI_CR_OFFSET);
+               /* ACK old irqs (if any) */
+               isr = xspi->read_fn(xspi->regs + XIPIF_V123B_IISR_OFFSET);
+               if (isr)
+                       xspi->write_fn(isr,
+                                      xspi->regs + XIPIF_V123B_IISR_OFFSET);
+               /* Enable the global IPIF interrupt */
+               xspi->write_fn(XIPIF_V123B_GINTR_ENABLE,
+                               xspi->regs + XIPIF_V123B_DGIER_OFFSET);
+               reinit_completion(&xspi->done);
        }
 
        while (remaining_words) {


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