1 files changed, 27 insertions, 10 deletions

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index bb758978465d..562ff83debd9 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -205,18 +205,30 @@ static void cdns_spi_chipselect(struct spi_device *spi, bool is_high)
 static void cdns_spi_config_clock_mode(struct spi_device *spi)
 {
         struct cdns_spi *xspi = spi_master_get_devdata(spi->master);
-        u32 ctrl_reg;
+        u32 ctrl_reg, new_ctrl_reg;
 
-        ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR_OFFSET);
+        new_ctrl_reg = ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR_OFFSET);
 
         /* Set the SPI clock phase and clock polarity */
-        ctrl_reg &= ~(CDNS_SPI_CR_CPHA_MASK | CDNS_SPI_CR_CPOL_MASK);
+        new_ctrl_reg &= ~(CDNS_SPI_CR_CPHA_MASK | CDNS_SPI_CR_CPOL_MASK);
         if (spi->mode & SPI_CPHA)
-                ctrl_reg |= CDNS_SPI_CR_CPHA_MASK;
+                new_ctrl_reg |= CDNS_SPI_CR_CPHA_MASK;
         if (spi->mode & SPI_CPOL)
-                ctrl_reg |= CDNS_SPI_CR_CPOL_MASK;
-
-        cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET, ctrl_reg);
+                new_ctrl_reg |= CDNS_SPI_CR_CPOL_MASK;
+
+        if (new_ctrl_reg != ctrl_reg) {
+                /*
+                 * Just writing the CR register does not seem to apply the clock
+                 * setting changes. This is problematic when changing the clock
+                 * polarity as it will cause the SPI slave to see spurious clock
+                 * transitions. To workaround the issue toggle the ER register.
+                 */
+                cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
+                                   CDNS_SPI_ER_DISABLE_MASK);
+                cdns_spi_write(xspi, CDNS_SPI_CR_OFFSET, new_ctrl_reg);
+                cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
+                                   CDNS_SPI_ER_ENABLE_MASK);
+        }
 }
 
 /**
@@ -370,6 +382,12 @@ static irqreturn_t cdns_spi_irq(int irq, void *dev_id)
 
         return status;
 }
+static int cdns_prepare_message(struct spi_master *master,
+                                struct spi_message *msg)
+{
+        cdns_spi_config_clock_mode(msg->spi);
+        return 0;
+}
 
 /**
  * cdns_transfer_one - Initiates the SPI transfer
@@ -416,8 +434,6 @@ static int cdns_prepare_transfer_hardware(struct spi_master *master)
 {
         struct cdns_spi *xspi = spi_master_get_devdata(master);
 
-        cdns_spi_config_clock_mode(master->cur_msg->spi);
-
         cdns_spi_write(xspi, CDNS_SPI_ER_OFFSET,
                        CDNS_SPI_ER_ENABLE_MASK);
 
@@ -532,6 +548,7 @@ static int cdns_spi_probe(struct platform_device *pdev)
                 xspi->is_decoded_cs = 0;
 
         master->prepare_transfer_hardware = cdns_prepare_transfer_hardware;
+        master->prepare_message = cdns_prepare_message;
         master->transfer_one = cdns_transfer_one;
         master->unprepare_transfer_hardware = cdns_unprepare_transfer_hardware;
         master->set_cs = cdns_spi_chipselect;
@@ -647,7 +664,7 @@ static int __maybe_unused cdns_spi_resume(struct device *dev)
 static SIMPLE_DEV_PM_OPS(cdns_spi_dev_pm_ops, cdns_spi_suspend,
                          cdns_spi_resume);
 
-static struct of_device_id cdns_spi_of_match[] = {
+static const struct of_device_id cdns_spi_of_match[] = {
         { .compatible = "xlnx,zynq-spi-r1p6" },
         { .compatible = "cdns,spi-r1p6" },
         { /* end of table */ }