clk: thead: add support for enabling/disabling PLLs

The 2nd control word of T-Head TH1520 PLLs contains a bit to put the VCO
into reset state, which means disabling the PLL.

Some PLLs are put to disabled state by the bootloader, and the clock
driver should be able to enable them.

Add support for enabling/disabling PLLs. PLLs other than DPU ones are
set CLK_IS_CRITICAL to prevent killing the system -- they're meant to
drive CPU or system buses (even the GMAC/Video ones are driving arbitrary
buses).

Signed-off-by: Icenowy Zheng <[e-mail]>
Reviewed-by: Drew Fustini <[e-mail]>
Signed-off-by: Drew Fustini <[e-mail]>

drivers/clk/thead/clk-th1520-ap.c

···
 #define TH1520_PLL_FBDIV	GENMASK(19, 8)
 #define TH1520_PLL_REFDIV	GENMASK(5, 0)
 #define TH1520_PLL_BYPASS	BIT(30)
+#define TH1520_PLL_VCO_RST	BIT(29)
 #define TH1520_PLL_DSMPD	BIT(24)
 #define TH1520_PLL_FRAC		GENMASK(23, 0)
 #define TH1520_PLL_FRAC_BITS    24
···
 	.determine_rate	= clk_hw_determine_rate_no_reparent,
 };
 
+static void ccu_pll_disable(struct clk_hw *hw)
+{
+	struct ccu_pll *pll = hw_to_ccu_pll(hw);
+
+	regmap_set_bits(pll->common.map, pll->common.cfg1,
+			TH1520_PLL_VCO_RST);
+}
+
+static int ccu_pll_enable(struct clk_hw *hw)
+{
+	struct ccu_pll *pll = hw_to_ccu_pll(hw);
+
+	return regmap_clear_bits(pll->common.map, pll->common.cfg1,
+				 TH1520_PLL_VCO_RST);
+}
+
+static int ccu_pll_is_enabled(struct clk_hw *hw)
+{
+	struct ccu_pll *pll = hw_to_ccu_pll(hw);
+
+	return !regmap_test_bits(pll->common.map, pll->common.cfg1,
+				 TH1520_PLL_VCO_RST);
+}
+
 static unsigned long th1520_pll_vco_recalc_rate(struct clk_hw *hw,
 						unsigned long parent_rate)
 {
···
 }
 
 static const struct clk_ops clk_pll_ops = {
+	.disable	= ccu_pll_disable,
+	.enable		= ccu_pll_enable,
+	.is_enabled	= ccu_pll_is_enabled,
 	.recalc_rate	= ccu_pll_recalc_rate,
 };
 
···
 		.hw.init	= CLK_HW_INIT_PARENTS_DATA("cpu-pll0",
 					      osc_24m_clk,
 					      &clk_pll_ops,
-					      0),
+					      CLK_IS_CRITICAL),
 	},
 };
 
···
 		.hw.init	= CLK_HW_INIT_PARENTS_DATA("cpu-pll1",
 					      osc_24m_clk,
 					      &clk_pll_ops,
-					      0),
+					      CLK_IS_CRITICAL),
 	},
 };
 
···
 		.hw.init	= CLK_HW_INIT_PARENTS_DATA("gmac-pll",
 					      osc_24m_clk,
 					      &clk_pll_ops,
-					      0),
+					      CLK_IS_CRITICAL),
 	},
 };
 
···
 		.hw.init	= CLK_HW_INIT_PARENTS_DATA("video-pll",
 					      osc_24m_clk,
 					      &clk_pll_ops,
-					      0),
+					      CLK_IS_CRITICAL),
 	},
 };
 
···
 		.hw.init	= CLK_HW_INIT_PARENTS_DATA("tee-pll",
 					      osc_24m_clk,
 					      &clk_pll_ops,
-					      0),
+					      CLK_IS_CRITICAL),
 	},
 };