Date:   Thu,  6 Aug 2020 18:06:46 +0200
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     linux-clk@...r.kernel.org
Cc:     tomasz.figa@...il.com, cw00.choi@...sung.com, sboyd@...nel.org,
        mturquette@...libre.com, linux-samsung-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, b.zolnierkie@...sung.com,
        m.szyprowski@...sung.com,
        Sylwester Nawrocki <s.nawrocki@...sung.com>
Subject: [PATCH] clk: samsung: Prevent potential endless loop in the PLL
 set_rate ops

In the .set_rate callback for some PLLs there is a loop polling state
of the PLL lock bit and it may become an endless loop when something
goes wrong with the PLL. For some PLLs there is already (duplicated)
code for polling with a timeout. This patch refactors that code a bit
and moves it to a common helper function which is then used
in .set_rate callbacks for all the PLLs.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
---
 drivers/clk/samsung/clk-pll.c | 94 +++++++++++++----------------------
 1 file changed, 35 insertions(+), 59 deletions(-)

diff --git a/drivers/clk/samsung/clk-pll.c b/drivers/clk/samsung/clk-pll.c
index ac70ad785d8e..0929644be99a 100644
--- a/drivers/clk/samsung/clk-pll.c
+++ b/drivers/clk/samsung/clk-pll.c
@@ -63,6 +63,27 @@ static long samsung_pll_round_rate(struct clk_hw *hw,
 	return rate_table[i - 1].rate;
 }
 
+static int samsung_pll_lock_wait(struct samsung_clk_pll *pll,
+				 unsigned int reg_mask)
+{
+	ktime_t timeout;
+
+	/* Wait until the PLL is in steady locked state */
+	timeout = ktime_add_ms(ktime_get(), PLL_TIMEOUT_MS);
+
+	while (!(readl_relaxed(pll->con_reg) & reg_mask)) {
+		if (ktime_after(ktime_get(), timeout)) {
+			pr_err("%s: Could not lock PLL %s\n",
+				__func__, clk_hw_get_name(&pll->hw));
+			return -EFAULT;
+		}
+
+		cpu_relax();
+	}
+
+	return 0;
+}
+
 static int samsung_pll3xxx_enable(struct clk_hw *hw)
 {
 	struct samsung_clk_pll *pll = to_clk_pll(hw);
@@ -241,12 +262,9 @@ static int samsung_pll35xx_set_rate(struct clk_hw *hw, unsigned long drate,
 	writel_relaxed(tmp, pll->con_reg);
 
 	/* Wait until the PLL is locked if it is enabled. */
-	if (tmp & BIT(pll->enable_offs)) {
-		do {
-			cpu_relax();
-			tmp = readl_relaxed(pll->con_reg);
-		} while (!(tmp & BIT(pll->lock_offs)));
-	}
+	if (tmp & BIT(pll->enable_offs))
+		return samsung_pll_lock_wait(pll, BIT(pll->lock_offs));
+
 	return 0;
 }
 
@@ -318,7 +336,7 @@ static int samsung_pll36xx_set_rate(struct clk_hw *hw, unsigned long drate,
 					unsigned long parent_rate)
 {
 	struct samsung_clk_pll *pll = to_clk_pll(hw);
-	u32 tmp, pll_con0, pll_con1;
+	u32 pll_con0, pll_con1;
 	const struct samsung_pll_rate_table *rate;
 
 	rate = samsung_get_pll_settings(pll, drate);
@@ -356,13 +374,8 @@ static int samsung_pll36xx_set_rate(struct clk_hw *hw, unsigned long drate,
 	pll_con1 |= rate->kdiv << PLL36XX_KDIV_SHIFT;
 	writel_relaxed(pll_con1, pll->con_reg + 4);
 
-	/* wait_lock_time */
-	if (pll_con0 & BIT(pll->enable_offs)) {
-		do {
-			cpu_relax();
-			tmp = readl_relaxed(pll->con_reg);
-		} while (!(tmp & BIT(pll->lock_offs)));
-	}
+	if (pll_con0 & BIT(pll->enable_offs))
+		return samsung_pll_lock_wait(pll, BIT(pll->lock_offs));
 
 	return 0;
 }
@@ -437,7 +450,6 @@ static int samsung_pll45xx_set_rate(struct clk_hw *hw, unsigned long drate,
 	struct samsung_clk_pll *pll = to_clk_pll(hw);
 	const struct samsung_pll_rate_table *rate;
 	u32 con0, con1;
-	ktime_t start;
 
 	/* Get required rate settings from table */
 	rate = samsung_get_pll_settings(pll, drate);
@@ -489,20 +501,7 @@ static int samsung_pll45xx_set_rate(struct clk_hw *hw, unsigned long drate,
 	writel_relaxed(con0, pll->con_reg);
 
 	/* Wait for locking. */
-	start = ktime_get();
-	while (!(readl_relaxed(pll->con_reg) & PLL45XX_LOCKED)) {
-		ktime_t delta = ktime_sub(ktime_get(), start);
-
-		if (ktime_to_ms(delta) > PLL_TIMEOUT_MS) {
-			pr_err("%s: could not lock PLL %s\n",
-					__func__, clk_hw_get_name(hw));
-			return -EFAULT;
-		}
-
-		cpu_relax();
-	}
-
-	return 0;
+	return samsung_pll_lock_wait(pll, PLL45XX_LOCKED);
 }
 
 static const struct clk_ops samsung_pll45xx_clk_ops = {
@@ -588,7 +587,6 @@ static int samsung_pll46xx_set_rate(struct clk_hw *hw, unsigned long drate,
 	struct samsung_clk_pll *pll = to_clk_pll(hw);
 	const struct samsung_pll_rate_table *rate;
 	u32 con0, con1, lock;
-	ktime_t start;
 
 	/* Get required rate settings from table */
 	rate = samsung_get_pll_settings(pll, drate);
@@ -648,20 +646,7 @@ static int samsung_pll46xx_set_rate(struct clk_hw *hw, unsigned long drate,
 	writel_relaxed(con1, pll->con_reg + 0x4);
 
 	/* Wait for locking. */
-	start = ktime_get();
-	while (!(readl_relaxed(pll->con_reg) & PLL46XX_LOCKED)) {
-		ktime_t delta = ktime_sub(ktime_get(), start);
-
-		if (ktime_to_ms(delta) > PLL_TIMEOUT_MS) {
-			pr_err("%s: could not lock PLL %s\n",
-					__func__, clk_hw_get_name(hw));
-			return -EFAULT;
-		}
-
-		cpu_relax();
-	}
-
-	return 0;
+	return samsung_pll_lock_wait(pll, PLL46XX_LOCKED);
 }
 
 static const struct clk_ops samsung_pll46xx_clk_ops = {
@@ -1035,14 +1020,9 @@ static int samsung_pll2550xx_set_rate(struct clk_hw *hw, unsigned long drate,
 			(rate->sdiv << PLL2550XX_S_SHIFT);
 	writel_relaxed(tmp, pll->con_reg);
 
-	/* wait_lock_time */
-	do {
-		cpu_relax();
-		tmp = readl_relaxed(pll->con_reg);
-	} while (!(tmp & (PLL2550XX_LOCK_STAT_MASK
-			<< PLL2550XX_LOCK_STAT_SHIFT)));
-
-	return 0;
+	/* Wait for locking. */
+	return samsung_pll_lock_wait(pll,
+			PLL2550XX_LOCK_STAT_MASK << PLL2550XX_LOCK_STAT_SHIFT);
 }
 
 static const struct clk_ops samsung_pll2550xx_clk_ops = {
@@ -1132,13 +1112,9 @@ static int samsung_pll2650x_set_rate(struct clk_hw *hw, unsigned long drate,
 	con1 |= ((rate->kdiv & PLL2650X_K_MASK) << PLL2650X_K_SHIFT);
 	writel_relaxed(con1, pll->con_reg + 4);
 
-	do {
-		cpu_relax();
-		con0 = readl_relaxed(pll->con_reg);
-	} while (!(con0 & (PLL2650X_LOCK_STAT_MASK
-			<< PLL2650X_LOCK_STAT_SHIFT)));
-
-	return 0;
+	/* Wait for locking. */
+	return samsung_pll_lock_wait(pll,
+			PLL2650X_LOCK_STAT_MASK << PLL2650X_LOCK_STAT_SHIFT);
 }
 
 static const struct clk_ops samsung_pll2650x_clk_ops = {
-- 
2.17.1

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