[PATCH v1] drivers: cadence_qspi_apb: Add 1us delays in polling loops

[Boon Khai Ng]

Add 1us delays in busy-wait polling loops to reduce CPU usage, minimize
bus traffic, and prevent watchdog timeout during QSPI operations.

Three tight polling loops continuously check hardware status without
any delay, consuming excessive CPU cycles and potentially triggering
watchdog timeout on long operations. Adding small delays allows the
hardware time to respond and reduces unnecessary register reads.

The udelay() function includes WATCHDOG_RESET()/schedule() calls that
service the watchdog, preventing system reset during extended QSPI
transfers.

Signed-off-by: Boon Khai Ng <boon.khai.ng at altera.com>
---
 drivers/spi/cadence_qspi_apb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/spi/cadence_qspi_apb.c b/drivers/spi/cadence_qspi_apb.c
index 0d4bc685f5d..ef03b263e14 100644
--- a/drivers/spi/cadence_qspi_apb.c
+++ b/drivers/spi/cadence_qspi_apb.c
@@ -157,6 +157,7 @@ static unsigned int cadence_qspi_wait_idle(void *reg_base)
 
 	start = get_timer(0);
 	for ( ; get_timer(start) < timeout ; ) {
+		udelay(1);
 		if (CQSPI_REG_IS_IDLE(reg_base))
 			count++;
 		else
@@ -728,6 +729,7 @@ cadence_qspi_apb_indirect_read_execute(struct cadence_spi_priv *priv,
 			rxbuf += bytes_to_read;
 			remaining -= bytes_to_read;
 			bytes_to_read = cadence_qspi_get_rd_sram_level(priv);
+			udelay(1);
 		}
 	}
 
@@ -898,6 +900,7 @@ cadence_qspi_apb_indirect_write_execute(struct cadence_spi_priv *priv,
 
 		bb_txbuf += write_bytes;
 		remaining -= write_bytes;
+		udelay(1);
 	}
 
 	/* Check indirect done status */
-- 
2.43.7