[U-Boot] [PATCH 1/4] spi: cadence_qspi: Ensure spi_calibration is run when sclk change

[Chin Liang See]

Ensuring spi_calibration is run when there is a change of sclk
frequency. This will ensure the qspi flash access works for high
sclk frequency

Signed-off-by: Chin Liang See <clsee at altera.com>
Cc: Dinh Nguyen <dinguyen at opensource.altera.com>
Cc: Dinh Nguyen <dinh.linux at gmail.com>
Cc: Marek Vasut <marex at denx.de>
Cc: Stefan Roese <sr at denx.de>
Cc: Vikas Manocha <vikas.manocha at st.com>
Cc: Jagannadh Teki <jteki at openedev.com>
Cc: Pavel Machek <pavel at denx.de>
---
Changes for v2
- remove frequency set before calibration
- introducing previous_hz to store requested frequency
- prevent calibration run when request same frequency
---
 drivers/spi/cadence_qspi.c |   19 ++++++++++++-------
 drivers/spi/cadence_qspi.h |    1 +
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/spi/cadence_qspi.c b/drivers/spi/cadence_qspi.c
index 34a0f46..23c88d5 100644
--- a/drivers/spi/cadence_qspi.c
+++ b/drivers/spi/cadence_qspi.c
@@ -37,7 +37,7 @@ static int cadence_spi_write_speed(struct udevice *bus, uint hz)
 }
 
 /* Calibration sequence to determine the read data capture delay register */
-static int spi_calibration(struct udevice *bus)
+static int spi_calibration(struct udevice *bus, uint hz)
 {
 	struct cadence_spi_platdata *plat = bus->platdata;
 	struct cadence_spi_priv *priv = dev_get_priv(bus);
@@ -46,6 +46,10 @@ static int spi_calibration(struct udevice *bus)
 	unsigned int idcode = 0, temp = 0;
 	int err = 0, i, range_lo = -1, range_hi = -1;
 
+	/* if calibrated frequency same as reqeusted, skip it */
+	if (priv->qspi_calibrated_hz == hz)
+		return 0;
+
 	/* start with slowest clock (1 MHz) */
 	cadence_spi_write_speed(bus, 1000000);
 
@@ -64,7 +68,7 @@ static int spi_calibration(struct udevice *bus)
 	}
 
 	/* use back the intended clock and find low range */
-	cadence_spi_write_speed(bus, plat->max_hz);
+	cadence_spi_write_speed(bus, hz);
 	for (i = 0; i < CQSPI_READ_CAPTURE_MAX_DELAY; i++) {
 		/* Disable QSPI */
 		cadence_qspi_apb_controller_disable(base);
@@ -111,7 +115,7 @@ static int spi_calibration(struct udevice *bus)
 	      (range_hi + range_lo) / 2, range_lo, range_hi);
 
 	/* just to ensure we do once only when speed or chip select change */
-	priv->qspi_calibrated_hz = plat->max_hz;
+	priv->qspi_calibrated_hz = hz;
 	priv->qspi_calibrated_cs = spi_chip_select(bus);
 
 	return 0;
@@ -126,14 +130,15 @@ static int cadence_spi_set_speed(struct udevice *bus, uint hz)
 	/* Disable QSPI */
 	cadence_qspi_apb_controller_disable(priv->regbase);
 
-	cadence_spi_write_speed(bus, hz);
-
 	/* Calibration required for different SCLK speed or chip select */
-	if (priv->qspi_calibrated_hz != plat->max_hz ||
+	if (priv->previous_hz != hz ||
 	    priv->qspi_calibrated_cs != spi_chip_select(bus)) {
-		err = spi_calibration(bus);
+		err = spi_calibration(bus, hz);
 		if (err)
 			return err;
+
+		/* prevent calibration run when same as previous request */
+		priv->previous_hz = hz;
 	}
 
 	/* Enable QSPI */
diff --git a/drivers/spi/cadence_qspi.h b/drivers/spi/cadence_qspi.h
index 98e57aa..2912e36 100644
--- a/drivers/spi/cadence_qspi.h
+++ b/drivers/spi/cadence_qspi.h
@@ -38,6 +38,7 @@ struct cadence_spi_priv {
 	int		qspi_is_init;
 	unsigned int	qspi_calibrated_hz;
 	unsigned int	qspi_calibrated_cs;
+	unsigned int	previous_hz;
 };
 
 /* Functions call declaration */
-- 
1.7.7.4