H616 CPU clock notifier patch, to reparent CPU to PLL_PERI0 during DVFS frequency change

clk_sunxi-ng_h616_cpu_notifier.patch

commit 5791b78a20997f5bae3e8c5fbdd444dc6a692ae9
Author: Andre Przywara <[email protected]>
Date:   Thu Oct 24 01:25:45 2024 +0100

    clk: sunxi-ng: h616: Reparent CPU clock during frequency changes
    
    The H616 user manual recommends to re-parent the CPU clock during
    frequency changes of the PLL, and recommends PLL_PERI0(1X), which runs
    at 600 MHz.
    
    Add a clock notifier for the PLL, using the existing mux clock notifier
    callback, and tell it to use mux 4 (the PLL_PERI0(1X) source).
    
    The manual also tells us to re-lock the PLL, though this needs to be
    done elsewhere.
    
    Signed-off-by: Andre Przywara <[email protected]>

diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-h616.c b/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
index b758993ee45a0..1c9705461920c 100644
--- a/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
+++ b/drivers/clk/sunxi-ng/ccu-sun50i-h616.c
@@ -1100,11 +1100,18 @@ static const u32 usb2_clk_regs[] = {
 	SUN50I_H616_USB3_CLK_REG,
 };
 
+static struct ccu_mux_nb sun50i_h616_cpu_nb = {
+	.common		= &cpux_clk.common,
+	.cm		= &cpux_clk.mux,
+	.delay_us	= 1, /* manual doesn't really say */
+	.bypass_index	= 4, /* PLL_PERI0(1X)@600MHz, as recommended by manual */
+};
+
 static int sun50i_h616_ccu_probe(struct platform_device *pdev)
 {
 	void __iomem *reg;
 	u32 val;
-	int i;
+	int ret, i;
 
 	reg = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(reg))
@@ -1154,7 +1161,15 @@ static int sun50i_h616_ccu_probe(struct platform_device *pdev)
 	val |= BIT(24);
 	writel(val, reg + SUN50I_H616_HDMI_CEC_CLK_REG);
 
-	return devm_sunxi_ccu_probe(&pdev->dev, reg, &sun50i_h616_ccu_desc);
+	ret = devm_sunxi_ccu_probe(&pdev->dev, reg, &sun50i_h616_ccu_desc);
+	if (ret)
+		return ret;
+
+	/* Reparent CPU during PLL CPU rate changes */
+	ccu_mux_notifier_register(pll_cpux_clk.common.hw.clk,
+				  &sun50i_h616_cpu_nb);
+
+	return 0;
 }
 
 static const struct of_device_id sun50i_h616_ccu_ids[] = {