[PATCH v4 1/2] clk: starfive: jh7110-sys: Add notifier for PLL clock

[Xingyu Wu]

Add notifier function for PLL clock. In the function, the cpu_root clock
should be operated by saving its current parent and setting a new safe
parent (osc clock) before setting the PLL clock rate. After setting PLL
rate, it should be switched back to the original parent clock.

Signed-off-by: Xingyu Wu <xingyu.wu at starfivetech.com>
---
 .../clk/starfive/clk-starfive-jh7110-sys.c    | 31 ++++++++++++++++++-
 drivers/clk/starfive/clk-starfive-jh71x0.h    |  2 ++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/starfive/clk-starfive-jh7110-sys.c b/drivers/clk/starfive/clk-starfive-jh7110-sys.c
index 8f5e5abfa178..adf62e4d94e4 100644
--- a/drivers/clk/starfive/clk-starfive-jh7110-sys.c
+++ b/drivers/clk/starfive/clk-starfive-jh7110-sys.c
@@ -385,6 +385,32 @@ int jh7110_reset_controller_register(struct jh71x0_clk_priv *priv,
 }
 EXPORT_SYMBOL_GPL(jh7110_reset_controller_register);
 
+/*
+ * This clock notifier is called when the rate of PLL0 clock is to be change,
+ * The cpu_root clock should save curent parent clock and swicth its parent
+ * clock to osc before PLL0 rate will be changed. And switch its parent clock
+ * back after PLL rate finished.
+ */
+static int jh7110_pll_clk_notifier_cb(struct notifier_block *nb,
+				      unsigned long action, void *data)
+{
+	struct jh71x0_clk_priv *priv = container_of(nb, struct jh71x0_clk_priv, pll_clk_nb);
+	struct clk *cpu_root = priv->reg[JH7110_SYSCLK_CPU_ROOT].hw.clk;
+	int ret = 0;
+
+	if (action == PRE_RATE_CHANGE) {
+		struct clk *osc = clk_get(priv->dev, "osc");
+
+		priv->original_clk = clk_get_parent(cpu_root);
+		ret = clk_set_parent(cpu_root, osc);
+		clk_put(osc);
+	} else if (action == POST_RATE_CHANGE) {
+		ret = clk_set_parent(cpu_root, priv->original_clk);
+	}
+
+	return notifier_from_errno(ret);
+}
+
 static int __init jh7110_syscrg_probe(struct platform_device *pdev)
 {
 	struct jh71x0_clk_priv *priv;
@@ -413,7 +439,10 @@ static int __init jh7110_syscrg_probe(struct platform_device *pdev)
 		if (IS_ERR(priv->pll[0]))
 			return PTR_ERR(priv->pll[0]);
 	} else {
-		clk_put(pllclk);
+		priv->pll_clk_nb.notifier_call = jh7110_pll_clk_notifier_cb;
+		ret = clk_notifier_register(pllclk, &priv->pll_clk_nb);
+		if (ret)
+			return ret;
 		priv->pll[0] = NULL;
 	}
 
diff --git a/drivers/clk/starfive/clk-starfive-jh71x0.h b/drivers/clk/starfive/clk-starfive-jh71x0.h
index 23e052fc1549..e3f441393e48 100644
--- a/drivers/clk/starfive/clk-starfive-jh71x0.h
+++ b/drivers/clk/starfive/clk-starfive-jh71x0.h
@@ -114,6 +114,8 @@ struct jh71x0_clk_priv {
 	spinlock_t rmw_lock;
 	struct device *dev;
 	void __iomem *base;
+	struct clk *original_clk;
+	struct notifier_block pll_clk_nb;
 	struct clk_hw *pll[3];
 	struct jh71x0_clk reg[];
 };
-- 
2.25.1