clk: thead: th1520-ap: Poll for PLL lock and wait for stability

All PLLs found on TH1520 SoC take 21250ns at maximum to lock, and their
lock status is indicated by register PLL_STS (offset 0x80 inside AP
clock controller). We should poll the register to ensure the PLL
actually locks after enabling it.

Furthermore, a 30us delay is added after enabling the PLL, after which
the PLL could be considered stable as stated by vendor clock code.

Fixes: 56a48c1833aa ("clk: thead: add support for enabling/disabling PLLs")
Reviewed-by: Drew Fustini <fustini@kernel.org>
Signed-off-by: Yao Zi <ziyao@disroot.org>
Signed-off-by: Drew Fustini <fustini@kernel.org>

diff --git a/drivers/clk/thead/clk-th1520-ap.c b/drivers/clk/thead/clk-th1520-ap.c
index 71ad03a998e8e19f7a551325573c964aaea217c0..d870f0c665f8a4f68dfb4025708fe0a27eed1eaa 100644 (file)
--- a/drivers/clk/thead/clk-th1520-ap.c
+++ b/drivers/clk/thead/clk-th1520-ap.c
@@ -8,11 +8,14 @@
 #include <dt-bindings/clock/thead,th1520-clk-ap.h>
 #include <linux/bitfield.h>
 #include <linux/clk-provider.h>
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 
+#define TH1520_PLL_STS         0x80
+
 #define TH1520_PLL_POSTDIV2    GENMASK(26, 24)
 #define TH1520_PLL_POSTDIV1    GENMASK(22, 20)
 #define TH1520_PLL_FBDIV       GENMASK(19, 8)
@@ -23,6 +26,13 @@
 #define TH1520_PLL_FRAC                GENMASK(23, 0)
 #define TH1520_PLL_FRAC_BITS    24
 
+/*
+ * All PLLs in TH1520 take 21250ns at maximum to lock, let's take its double
+ * for safety.
+ */
+#define TH1520_PLL_LOCK_TIMEOUT_US     44
+#define TH1520_PLL_STABLE_DELAY_US     30
+
 struct ccu_internal {
        u8      shift;
        u8      width;
@@ -64,6 +74,7 @@ struct ccu_div {
 
 struct ccu_pll {
        struct ccu_common       common;
+       u32                     lock_sts_mask;
 };
 
 #define TH_CCU_ARG(_shift, _width)                                     \
@@ -299,9 +310,21 @@ static void ccu_pll_disable(struct clk_hw *hw)
 static int ccu_pll_enable(struct clk_hw *hw)
 {
        struct ccu_pll *pll = hw_to_ccu_pll(hw);
+       u32 reg;
+       int ret;
 
-       return regmap_clear_bits(pll->common.map, pll->common.cfg1,
-                                TH1520_PLL_VCO_RST);
+       regmap_clear_bits(pll->common.map, pll->common.cfg1,
+                         TH1520_PLL_VCO_RST);
+
+       ret = regmap_read_poll_timeout_atomic(pll->common.map, TH1520_PLL_STS,
+                                             reg, reg & pll->lock_sts_mask,
+                                             5, TH1520_PLL_LOCK_TIMEOUT_US);
+       if (ret)
+               return ret;
+
+       udelay(TH1520_PLL_STABLE_DELAY_US);
+
+       return 0;
 }
 
 static int ccu_pll_is_enabled(struct clk_hw *hw)
@@ -389,6 +412,7 @@ static struct ccu_pll cpu_pll0_clk = {
                                              &clk_pll_ops,
                                              CLK_IS_CRITICAL),
        },
+       .lock_sts_mask          = BIT(1),
 };
 
 static struct ccu_pll cpu_pll1_clk = {
@@ -401,6 +425,7 @@ static struct ccu_pll cpu_pll1_clk = {
                                              &clk_pll_ops,
                                              CLK_IS_CRITICAL),
        },
+       .lock_sts_mask          = BIT(4),
 };
 
 static struct ccu_pll gmac_pll_clk = {
@@ -413,6 +438,7 @@ static struct ccu_pll gmac_pll_clk = {
                                              &clk_pll_ops,
                                              CLK_IS_CRITICAL),
        },
+       .lock_sts_mask          = BIT(3),
 };
 
 static const struct clk_hw *gmac_pll_clk_parent[] = {
@@ -433,6 +459,7 @@ static struct ccu_pll video_pll_clk = {
                                              &clk_pll_ops,
                                              CLK_IS_CRITICAL),
        },
+       .lock_sts_mask          = BIT(7),
 };
 
 static const struct clk_hw *video_pll_clk_parent[] = {
@@ -453,6 +480,7 @@ static struct ccu_pll dpu0_pll_clk = {
                                              &clk_pll_ops,
                                              0),
        },
+       .lock_sts_mask          = BIT(8),
 };
 
 static const struct clk_hw *dpu0_pll_clk_parent[] = {
@@ -469,6 +497,7 @@ static struct ccu_pll dpu1_pll_clk = {
                                              &clk_pll_ops,
                                              0),
        },
+       .lock_sts_mask          = BIT(9),
 };
 
 static const struct clk_hw *dpu1_pll_clk_parent[] = {
@@ -485,6 +514,7 @@ static struct ccu_pll tee_pll_clk = {
                                              &clk_pll_ops,
                                              CLK_IS_CRITICAL),
        },
+       .lock_sts_mask          = BIT(10),
 };
 
 static const struct clk_parent_data c910_i0_parents[] = {