[PATCH v10 13/19] spi: cadence-quadspi: reprogram CS timing on every chip-select switch

[Santhosh Kumar K <s-k6@ti.com>]

cqspi_configure() only reprogrammed per-device CS timing (CQSPI_REG_DELAY)
and the non-PHY read-capture register when the clock frequency changed, not
when the chip-select changed. In a multi-device setup where both devices
operate at the same frequency, a CS switch leaves the previous device's
timing parameters in hardware.

Split the update condition: baud rate divisor is updated on clock change
only (it is frequency-derived), but the per-device delay and read-capture
registers are now updated on any CS or clock switch.

Signed-off-by: Santhosh Kumar K <s-k6@ti.com>
---
 drivers/spi/spi-cadence-quadspi.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-cadence-quadspi.c b/drivers/spi/spi-cadence-quadspi.c
index 2752e7cce16c..10a393105ca1 100644
--- a/drivers/spi/spi-cadence-quadspi.c
+++ b/drivers/spi/spi-cadence-quadspi.c
@@ -1621,8 +1621,9 @@ static void cqspi_configure(struct cqspi_flash_pdata *f_pdata,
 	struct cqspi_st *cqspi = f_pdata->cqspi;
 	int switch_cs = (cqspi->current_cs != f_pdata->cs);
 	int switch_ck = (cqspi->sclk != sclk);
+	bool reconfigure = switch_cs || switch_ck;
 
-	if (switch_cs || switch_ck)
+	if (reconfigure)
 		cqspi_controller_enable(cqspi, 0);
 
 	/* Switch chip select. */
@@ -1631,17 +1632,26 @@ static void cqspi_configure(struct cqspi_flash_pdata *f_pdata,
 		cqspi_chipselect(f_pdata);
 	}
 
-	/* Setup baudrate divisor and delays */
+	/* Update baudrate only on clock change. */
 	if (switch_ck) {
 		cqspi->sclk = sclk;
 		cqspi_config_baudrate_div(cqspi);
+	}
+
+	/*
+	 * Reprogram per-device CS timing and non-PHY read capture on any
+	 * chip-select or clock switch. Without this, two devices at the same
+	 * frequency would each see the other's timing parameters after a CS
+	 * switch, since the lazy clock-only check would never trigger.
+	 */
+	if (reconfigure) {
 		cqspi_delay(f_pdata);
 		if (!cqspi->phy_tuning_active)
 			cqspi_readdata_capture(cqspi, !cqspi->rclk_en, false,
 					       f_pdata->read_delay);
 	}
 
-	if (switch_cs || switch_ck)
+	if (reconfigure)
 		cqspi_controller_enable(cqspi, 1);
 }
 
-- 
2.34.1