mux: mmio: Do not use syscon helper to build regmap

The syscon helper device_node_to_regmap() is used to fetch a regmap
registered to a device node. It also currently creates this regmap
if the node did not already have a regmap associated with it. This
should only be used on "syscon" nodes. This driver is not such a
device and instead uses device_node_to_regmap() on its own node as
a hacky way to create a regmap for itself.

This will not work going forward and so we should create our regmap
the normal way by defining our regmap_config, fetching our memory
resource, then using the normal regmap_init_mmio() function.

Signed-off-by: Andrew Davis <afd@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20250123182059.597491-1-afd@ti.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Author: glneo

drivers/mux/mmio.c

@@ -33,21 +33,32 @@ static const struct of_device_id mux_mmio_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, mux_mmio_dt_ids);
 
+static const struct regmap_config mux_mmio_regmap_cfg = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+};
+
 static int mux_mmio_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
 	struct regmap_field **fields;
 	struct mux_chip *mux_chip;
 	struct regmap *regmap;
+	void __iomem *base;
 	int num_fields;
 	int ret;
 	int i;
 
 	if (of_device_is_compatible(np, "mmio-mux")) {
 		regmap = syscon_node_to_regmap(np->parent);
 	} else {
-		regmap = device_node_to_regmap(np);
+		base = devm_platform_ioremap_resource(pdev, 0);
+		if (IS_ERR(base))
+			regmap = ERR_PTR(-ENODEV);
+		else
+			regmap = regmap_init_mmio(dev, base, &mux_mmio_regmap_cfg);
 		/* Fallback to checking the parent node on "real" errors. */
 		if (IS_ERR(regmap) && regmap != ERR_PTR(-EPROBE_DEFER)) {
 			regmap = dev_get_regmap(dev->parent, NULL);