spi: spi-zynqmp-gqspi: transmit dummy circles by using the controller's internal...

There is a data corruption issue that occurs in the reading operation
(cmd:0x6c) when transmitting common data as dummy circles.

The gqspi controller has the functionality to send dummy clock circles.
When writing data with the fields [receive, transmit, data_xfer] = [0,0,1]
to the Generic FIFO, and configuring the correct SPI mode, the controller
will transmit dummy circles.

So let's switch to hardware dummy cycles transfer to fix this issue.

Fixes: 1c26372e5aa9 ("spi: spi-zynqmp-gqspi: Update driver to use spi-mem framework")
Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
Reviewed-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com>
Link: https://lore.kernel.org/r/20210408040223.23134-4-quanyang.wang@windriver.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-zynqmp-gqspi.c b/drivers/spi/spi-zynqmp-gqspi.c
index 3b39461..cf73a06 100644 (file)
--- a/drivers/spi/spi-zynqmp-gqspi.c
+++ b/drivers/spi/spi-zynqmp-gqspi.c
@@ -521,7 +521,7 @@ static void zynqmp_qspi_filltxfifo(struct zynqmp_qspi *xqspi, int size)
 {
        u32 count = 0, intermediate;
 
-       while ((xqspi->bytes_to_transfer > 0) && (count < size)) {
+       while ((xqspi->bytes_to_transfer > 0) && (count < size) && (xqspi->txbuf)) {
                memcpy(&intermediate, xqspi->txbuf, 4);
                zynqmp_gqspi_write(xqspi, GQSPI_TXD_OFST, intermediate);
 
@@ -580,7 +580,7 @@ static void zynqmp_qspi_fillgenfifo(struct zynqmp_qspi *xqspi, u8 nbits,
                genfifoentry |= GQSPI_GENFIFO_DATA_XFER;
                genfifoentry |= GQSPI_GENFIFO_TX;
                transfer_len = xqspi->bytes_to_transfer;
-       } else {
+       } else if (xqspi->rxbuf) {
                genfifoentry &= ~GQSPI_GENFIFO_TX;
                genfifoentry |= GQSPI_GENFIFO_DATA_XFER;
                genfifoentry |= GQSPI_GENFIFO_RX;
@@ -588,6 +588,11 @@ static void zynqmp_qspi_fillgenfifo(struct zynqmp_qspi *xqspi, u8 nbits,
                        transfer_len = xqspi->dma_rx_bytes;
                else
                        transfer_len = xqspi->bytes_to_receive;
+       } else {
+               /* Sending dummy circles here */
+               genfifoentry &= ~(GQSPI_GENFIFO_TX | GQSPI_GENFIFO_RX);
+               genfifoentry |= GQSPI_GENFIFO_DATA_XFER;
+               transfer_len = xqspi->bytes_to_transfer;
        }
        genfifoentry |= zynqmp_qspi_selectspimode(xqspi, nbits);
        xqspi->genfifoentry = genfifoentry;
@@ -1011,32 +1016,23 @@ static int zynqmp_qspi_exec_op(struct spi_mem *mem,
        }
 
        if (op->dummy.nbytes) {
-               tmpbuf = kzalloc(op->dummy.nbytes, GFP_KERNEL | GFP_DMA);
-               if (!tmpbuf)
-                       return -ENOMEM;
-               memset(tmpbuf, 0xff, op->dummy.nbytes);
-               reinit_completion(&xqspi->data_completion);
-               xqspi->txbuf = tmpbuf;
+               xqspi->txbuf = NULL;
                xqspi->rxbuf = NULL;
-               xqspi->bytes_to_transfer = op->dummy.nbytes;
+               /*
+                * xqspi->bytes_to_transfer here represents the dummy circles
+                * which need to be sent.
+                */
+               xqspi->bytes_to_transfer = op->dummy.nbytes * 8 / op->dummy.buswidth;
                xqspi->bytes_to_receive = 0;
-               zynqmp_qspi_write_op(xqspi, op->dummy.buswidth,
+               /*
+                * Using op->data.buswidth instead of op->dummy.buswidth here because
+                * we need to use it to configure the correct SPI mode.
+                */
+               zynqmp_qspi_write_op(xqspi, op->data.buswidth,
                                     genfifoentry);
                zynqmp_gqspi_write(xqspi, GQSPI_CONFIG_OFST,
                                   zynqmp_gqspi_read(xqspi, GQSPI_CONFIG_OFST) |
                                   GQSPI_CFG_START_GEN_FIFO_MASK);
-               zynqmp_gqspi_write(xqspi, GQSPI_IER_OFST,
-                                  GQSPI_IER_TXEMPTY_MASK |
-                                  GQSPI_IER_GENFIFOEMPTY_MASK |
-                                  GQSPI_IER_TXNOT_FULL_MASK);
-               if (!wait_for_completion_interruptible_timeout
-                   (&xqspi->data_completion, msecs_to_jiffies(1000))) {
-                       err = -ETIMEDOUT;
-                       kfree(tmpbuf);
-                       goto return_err;
-               }
-
-               kfree(tmpbuf);
        }
 
        if (op->data.nbytes) {