spi: cadence-quadspi: Fix cqspi_setup_flash()

The 'max_cs' stores the largest chip select number. It should only
be updated when the current 'cs' is greater than existing 'max_cs'. So,
fix the condition accordingly.

Also, return failure if there are no flash device declared.

Fixes: 0f3841a ("spi: cadence-qspi: report correct number of chip-select")
CC: stable@vger.kernel.org
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Théo Lebrun <theo.lebrun@bootlin.com>
Signed-off-by: Santhosh Kumar K <s-k6@ti.com>
Message-ID: <20250905185958.3575037-4-s-k6@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Santhosh Kumar K

drivers/spi/spi-cadence-quadspi.c

@@ -1722,12 +1722,10 @@ static const struct spi_controller_mem_caps cqspi_mem_caps = {
 
 static int cqspi_setup_flash(struct cqspi_st *cqspi)
 {
-	unsigned int max_cs = cqspi->num_chipselect - 1;
 	struct platform_device *pdev = cqspi->pdev;
 	struct device *dev = &pdev->dev;
 	struct cqspi_flash_pdata *f_pdata;
-	unsigned int cs;
-	int ret;
+	int ret, cs, max_cs = -1;
 
 	/* Get flash device data */
 	for_each_available_child_of_node_scoped(dev->of_node, np) {
@@ -1740,10 +1738,10 @@ static int cqspi_setup_flash(struct cqspi_st *cqspi)
 		if (cs >= cqspi->num_chipselect) {
 			dev_err(dev, "Chip select %d out of range.\n", cs);
 			return -EINVAL;
-		} else if (cs < max_cs) {
-			max_cs = cs;
 		}
 
+		max_cs = max_t(int, cs, max_cs);
+
 		f_pdata = &cqspi->f_pdata[cs];
 		f_pdata->cqspi = cqspi;
 		f_pdata->cs = cs;
@@ -1753,6 +1751,11 @@ static int cqspi_setup_flash(struct cqspi_st *cqspi)
 			return ret;
 	}
 
+	if (max_cs < 0) {
+		dev_err(dev, "No flash device declared\n");
+		return -ENODEV;
+	}
+
 	cqspi->num_chipselect = max_cs + 1;
 	return 0;
 }