clk: samsung: Implement manual PLL control for ARM64 SoCs

Some ARM64 Exynos chips are capable to control PLL clocks automatically.
For those chips, whether the PLL is controlled automatically or manually
is chosen in PLL_CON1 register with next bits:

    [28]  ENABLE_AUTOMATIC_CLKGATING
    [1]   MANUAL_PLL_CTRL
    [0]   AUTO_PLL_CTRL

The bl2 bootloader sets 0x10000001 value for some PLL_CON1 registers,
which means any attempt to control those PLLs manually (e.g.
disabling/enabling those PLLs or changing MUX parent clocks) would lead
to PLL lock timeout with error message like this:

    Could not lock PLL ...

At the moment, all Samsung clock drivers implement manual clock control.
So in order to make it possible to control PLLs, corresponding PLL_CON1
registers should be set to 0x2 first.

Some older ARM64 chips don't implement the automatic clock control
though. It also might be desirable to configure some PLLs for manual
control, while keeping the default configuration for the rest. So it'd
convenient to choose this PLL mode for each CMU separately. Introduce
.manual_plls field to CMU structure to choose the PLL control mode.
Because it'll be initialized with "false" in all existing CMU
structures by default, it won't affect any existing clock drivers,
allowing for this feature to be enabled gradually when it's needed with
no change for the rest of users. In case .manual_plls is set, set
PLL_CON1 registers to manual control, akin to what's already done for
gate clocks in exynos_arm64_init_clocks(). Of course, PLL_CON1 registers
should be added to corresponding struct samsung_cmu_info::clk_regs array
to make sure they get initialized.

No functional change. This patch adds a feature, but doesn't enable it
for any users.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20240301015118.30072-1-semen.protsenko@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

drivers/clk/samsung/clk-exynos-arm64.c

@@ -17,10 +17,17 @@
 
 #include "clk-exynos-arm64.h"
 
+/* PLL register bits */
+#define PLL_CON1_MANUAL		BIT(1)
+
 /* Gate register bits */
 #define GATE_MANUAL		BIT(20)
 #define GATE_ENABLE_HWACG	BIT(28)
 
+/* PLL_CONx_PLL register offsets range */
+#define PLL_CON_OFF_START	0x100
+#define PLL_CON_OFF_END		0x600
+
 /* Gate register offsets range */
 #define GATE_OFF_START		0x2000
 #define GATE_OFF_END		0x2fff
@@ -38,17 +45,36 @@ struct exynos_arm64_cmu_data {
 	struct samsung_clk_provider *ctx;
 };
 
+/* Check if the register offset is a GATE register */
+static bool is_gate_reg(unsigned long off)
+{
+	return off >= GATE_OFF_START && off <= GATE_OFF_END;
+}
+
+/* Check if the register offset is a PLL_CONx register */
+static bool is_pll_conx_reg(unsigned long off)
+{
+	return off >= PLL_CON_OFF_START && off <= PLL_CON_OFF_END;
+}
+
+/* Check if the register offset is a PLL_CON1 register */
+static bool is_pll_con1_reg(unsigned long off)
+{
+	return is_pll_conx_reg(off) && (off & 0xf) == 0x4 && !(off & 0x10);
+}
+
 /**
  * exynos_arm64_init_clocks - Set clocks initial configuration
- * @np:			CMU device tree node with "reg" property (CMU addr)
- * @reg_offs:		Register offsets array for clocks to init
- * @reg_offs_len:	Number of register offsets in reg_offs array
+ * @np:		CMU device tree node with "reg" property (CMU addr)
+ * @cmu:	CMU data
  *
- * Set manual control mode for all gate clocks.
+ * Set manual control mode for all gate and PLL clocks.
  */
 static void __init exynos_arm64_init_clocks(struct device_node *np,
-		const unsigned long *reg_offs, size_t reg_offs_len)
+					    const struct samsung_cmu_info *cmu)
 {
+	const unsigned long *reg_offs = cmu->clk_regs;
+	size_t reg_offs_len = cmu->nr_clk_regs;
 	void __iomem *reg_base;
 	size_t i;
 
@@ -60,14 +86,14 @@ static void __init exynos_arm64_init_clocks(struct device_node *np,
 		void __iomem *reg = reg_base + reg_offs[i];
 		u32 val;
 
-		/* Modify only gate clock registers */
-		if (reg_offs[i] < GATE_OFF_START || reg_offs[i] > GATE_OFF_END)
-			continue;
-
-		val = readl(reg);
-		val |= GATE_MANUAL;
-		val &= ~GATE_ENABLE_HWACG;
-		writel(val, reg);
+		if (cmu->manual_plls && is_pll_con1_reg(reg_offs[i])) {
+			writel(PLL_CON1_MANUAL, reg);
+		} else if (is_gate_reg(reg_offs[i])) {
+			val = readl(reg);
+			val |= GATE_MANUAL;
+			val &= ~GATE_ENABLE_HWACG;
+			writel(val, reg);
+		}
 	}
 
 	iounmap(reg_base);
@@ -177,7 +203,7 @@ void __init exynos_arm64_register_cmu(struct device *dev,
 		pr_err("%s: could not enable bus clock %s; err = %d\n",
 		       __func__, cmu->clk_name, err);
 
-	exynos_arm64_init_clocks(np, cmu->clk_regs, cmu->nr_clk_regs);
+	exynos_arm64_init_clocks(np, cmu);
 	samsung_cmu_register_one(np, cmu);
 }
 
@@ -224,7 +250,7 @@ int __init exynos_arm64_register_cmu_pm(struct platform_device *pdev,
 		       __func__, cmu->clk_name, ret);
 
 	if (set_manual)
-		exynos_arm64_init_clocks(np, cmu->clk_regs, cmu->nr_clk_regs);
+		exynos_arm64_init_clocks(np, cmu);
 
 	reg_base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(reg_base))

drivers/clk/samsung/clk.h

@@ -330,6 +330,7 @@ struct samsung_clock_reg_cache {
  * @suspend_regs: list of clock registers to set before suspend
  * @nr_suspend_regs: count of clock registers in @suspend_regs
  * @clk_name: name of the parent clock needed for CMU register access
+ * @manual_plls: Enable manual control for PLL clocks
  */
 struct samsung_cmu_info {
 	const struct samsung_pll_clock *pll_clks;
@@ -354,6 +355,9 @@ struct samsung_cmu_info {
 	const struct samsung_clk_reg_dump *suspend_regs;
 	unsigned int nr_suspend_regs;
 	const char *clk_name;
+
+	/* ARM64 Exynos CMUs */
+	bool manual_plls;
 };
 
 struct samsung_clk_provider *samsung_clk_init(struct device *dev,