From bd8c8dcd4d6fb1cf726d5a267be5ec33c93f1471 Mon Sep 17 00:00:00 2001
From: Pratyush Yadav
Date: Sat, 26 Jun 2021 00:47:07 +0530
Subject: spi: cadence-qspi: Do not calibrate when device tree sets read delay
If the device tree provides a read delay value, use that directly and do
not perform the calibration procedure.
This allows the device tree to over-ride the read delay value in cases
where the read delay value obtained via calibration is incorrect. One
such example is the Cypress Semper flash. It needs a read delay of 4 in
octal DTR mode. But since the calibration procedure is run before the
flash is switched in octal DTR mode, it yields a read delay of 2. A
value of 4 works for both octal DTR and legacy modes.
Signed-off-by: Pratyush Yadav
Reviewed-by: Jagan Teki
---
drivers/spi/cadence_qspi.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
(limited to 'drivers/spi/cadence_qspi.c')
diff --git a/drivers/spi/cadence_qspi.c b/drivers/spi/cadence_qspi.c
index 67980431ba..de7628de27 100644
--- a/drivers/spi/cadence_qspi.c
+++ b/drivers/spi/cadence_qspi.c
@@ -141,12 +141,20 @@ static int cadence_spi_set_speed(struct udevice *bus, uint hz)
cadence_qspi_apb_controller_disable(priv->regbase);
/*
- * Calibration required for different current SCLK speed, requested
- * SCLK speed or chip select
+ * If the device tree already provides a read delay value, use that
+ * instead of calibrating.
*/
- if (priv->previous_hz != hz ||
- priv->qspi_calibrated_hz != hz ||
- priv->qspi_calibrated_cs != spi_chip_select(bus)) {
+ if (plat->read_delay >= 0) {
+ cadence_spi_write_speed(bus, hz);
+ cadence_qspi_apb_readdata_capture(priv->regbase, 1,
+ plat->read_delay);
+ } else if (priv->previous_hz != hz ||
+ priv->qspi_calibrated_hz != hz ||
+ priv->qspi_calibrated_cs != spi_chip_select(bus)) {
+ /*
+ * Calibration required for different current SCLK speed,
+ * requested SCLK speed or chip select
+ */
err = spi_calibration(bus, hz);
if (err)
return err;
@@ -320,6 +328,14 @@ static int cadence_spi_of_to_plat(struct udevice *bus)
255);
plat->tchsh_ns = ofnode_read_u32_default(subnode, "cdns,tchsh-ns", 20);
plat->tslch_ns = ofnode_read_u32_default(subnode, "cdns,tslch-ns", 20);
+ /*
+ * Read delay should be an unsigned value but we use a signed integer
+ * so that negative values can indicate that the device tree did not
+ * specify any signed values and we need to perform the calibration
+ * sequence to find it out.
+ */
+ plat->read_delay = ofnode_read_s32_default(subnode, "cdns,read-delay",
+ -1);
debug("%s: regbase=%p ahbbase=%p max-frequency=%d page-size=%d\n",
__func__, plat->regbase, plat->ahbbase, plat->max_hz,
--
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