soc: renesas: rzn1-sysc: Export function to set dmamux

The dmamux register is located within the system controller.

Without syscon, we need an extra helper in order to give write access to
this register to a dmamux driver.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/clk/renesas/r9a06g032-clocks.c

@@ -315,6 +315,27 @@ struct r9a06g032_priv {
 	void __iomem *reg;
 };
 
+/* Exported helper to access the DMAMUX register */
+static struct r9a06g032_priv *syscon_priv;
+int r9a06g032_syscon_set_dmamux(u32 mask, u32 val)
+{
+	u32 dmamux;
+
+	if (!syscon_priv)
+		return -EPROBE_DEFER;
+
+	spin_lock(&syscon_priv->lock);
+
+	dmamux = readl(syscon_priv->reg + R9A06G032_SYSCON_DMAMUX);
+	dmamux &= ~mask;
+	dmamux |= val & mask;
+	writel(dmamux, syscon_priv->reg + R9A06G032_SYSCON_DMAMUX);
+
+	spin_unlock(&syscon_priv->lock);
+
+	return 0;
+}
+
 /* register/bit pairs are encoded as an uint16_t */
 static void
 clk_rdesc_set(struct r9a06g032_priv *clocks,
@@ -922,6 +943,12 @@ static int __init r9a06g032_clocks_probe(struct platform_device *pdev)
 	clocks->reg = of_iomap(np, 0);
 	if (WARN_ON(!clocks->reg))
 		return -ENOMEM;
+
+	if (syscon_priv)
+		return -EBUSY;
+
+	syscon_priv = clocks;
+
 	for (i = 0; i < ARRAY_SIZE(r9a06g032_clocks); ++i) {
 		const struct r9a06g032_clkdesc *d = &r9a06g032_clocks[i];
 		const char *parent_name = d->source ?

include/dt-bindings/clock/r9a06g032-sysctrl.h

@@ -145,4 +145,6 @@
 #define R9A06G032_CLK_UART6		152
 #define R9A06G032_CLK_UART7		153
 
+#define R9A06G032_SYSCON_DMAMUX		0xA0
+
 #endif /* __DT_BINDINGS_R9A06G032_SYSCTRL_H__ */

include/linux/soc/renesas/r9a06g032-syscon.h

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_SOC_RENESAS_R9A06G032_SYSCON_H__
+#define __LINUX_SOC_RENESAS_R9A06G032_SYSCON_H__
+
+#ifdef CONFIG_CLK_R9A06G032
+int r9a06g032_syscon_set_dmamux(u32 mask, u32 val);
+#else
+static inline int r9a06g032_syscon_set_dmamux(u32 mask, u32 val) { return -ENODEV; }
+#endif
+
+#endif /* __LINUX_SOC_RENESAS_R9A06G032_SYSCON_H__ */