spi/fsl-espi: Make sure pm is within 2..32

The reference manual says that pm has to stay within 2 and 32. So the
lowest frequency is 32 and DIV16 set, the highest is 2 and DIV16 unset.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
index 43350f999314..7523a2429d09 100644
--- a/drivers/spi/spi-fsl-espi.c
+++ b/drivers/spi/spi-fsl-espi.c
@@ -182,16 +182,18 @@ static int fsl_espi_setup_transfer(struct spi_device *spi,
                 cs->hw_mode |= CSMODE_DIV16;
                 pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 16 * 4);
 
-                WARN_ONCE(pm > 16, "%s: Requested speed is too low: %d Hz. "
+                WARN_ONCE(pm > 33, "%s: Requested speed is too low: %d Hz. "
                           "Will use %d Hz instead.\n", dev_name(&spi->dev),
-                          hz, mpc8xxx_spi->spibrg / 1024);
-                if (pm > 16)
-                        pm = 16;
+                                hz, mpc8xxx_spi->spibrg / (4 * 16 * (32 + 1)));
+                if (pm > 33)
+                        pm = 33;
         } else {
                 pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 4);
         }
         if (pm)
                 pm--;
+        if (pm < 2)
+                pm = 2;
 
         cs->hw_mode |= CSMODE_PM(pm);