[PATCH 5/7] spi: atmel-quadspi: Allow setting SMM to classic SPI mode

[Alexander Dahl]

Switching between Serial Memory Mode (SMM) and (classic) SPI mode is a
preparation for implementing .xfer() in the future.

Signed-off-by: Alexander Dahl <a...@thorsis.com>
---
 drivers/spi/atmel-quadspi.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
index 467f29c01ca..d29b5ab96e9 100644
--- a/drivers/spi/atmel-quadspi.c
+++ b/drivers/spi/atmel-quadspi.c
@@ -479,15 +479,19 @@ static bool atmel_qspi_supports_op(struct spi_slave 
*slave,
 }
 
 /*
- * If the QSPI controller is set in regular SPI mode, set it in
- * Serial Memory Mode (SMM).
+ * Switch QSPI controller between regular SPI mode or Serial Memory Mode (SMM).
  */
-static int atmel_qspi_set_serial_memory_mode(struct atmel_qspi *aq)
+static int atmel_qspi_set_serial_memory_mode(struct atmel_qspi *aq,
+                                            bool enable)
 {
        int ret = 0;
 
-       if (!(aq->mr & QSPI_MR_SMM)) {
-               aq->mr |= QSPI_MR_SMM;
+       /* only write if designated state differs from current state */
+       if (!!(aq->mr & QSPI_MR_SMM) != enable) {
+               if (enable)
+                       aq->mr |= QSPI_MR_SMM;
+               else
+                       aq->mr &= ~QSPI_MR_SMM;
                atmel_qspi_write(aq->mr, aq, QSPI_MR);
 
                if (aq->caps->has_gclk)
@@ -576,7 +580,7 @@ static int atmel_qspi_set_cfg(struct atmel_qspi *aq,
                        ifr |= QSPI_IFR_TFRTYP_MEM;
        }
 
-       mode = atmel_qspi_set_serial_memory_mode(aq);
+       mode = atmel_qspi_set_serial_memory_mode(aq, true);
        if (mode < 0)
                return mode;
 
@@ -683,7 +687,7 @@ static int atmel_qspi_sama7g5_set_cfg(struct atmel_qspi *aq,
                        ifr |= QSPI_IFR_TFRTYP_MEM;
        }
 
-       ret = atmel_qspi_set_serial_memory_mode(aq);
+       ret = atmel_qspi_set_serial_memory_mode(aq, true);
        if (ret < 0)
                return ret;
 
@@ -910,7 +914,7 @@ static int atmel_qspi_sama7g5_set_speed(struct udevice 
*bus, uint hz)
 
        /* Set the QSPI controller by default in Serial Memory Mode */
        aq->mr |= QSPI_MR_DQSDLYEN;
-       ret = atmel_qspi_set_serial_memory_mode(aq);
+       ret = atmel_qspi_set_serial_memory_mode(aq, true);
        if (ret < 0)
                return ret;
 
-- 
2.39.5