linux-kernel - [PATCH v2] clk: samsung: clk-pll: simplify samsung_pll_lock

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Message-Id: <20251013-samsung-clk-pll-simplification-v2-1-b9aab610878c@linaro.org>
Date: Mon, 13 Oct 2025 06:27:16 +0100
From: André Draszik <andre.draszik@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>, 
 Sylwester Nawrocki <s.nawrocki@...sung.com>, 
 Chanwoo Choi <cw00.choi@...sung.com>, Alim Akhtar <alim.akhtar@...sung.com>, 
 Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>
Cc: Peter Griffin <peter.griffin@...aro.org>, 
 Tudor Ambarus <tudor.ambarus@...aro.org>, 
 Will McVicker <willmcvicker@...gle.com>, kernel-team@...roid.com, 
 linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Sam Protsenko <semen.protsenko@...aro.org>, 
 André Draszik <andre.draszik@...aro.org>
Subject: [PATCH v2] clk: samsung: clk-pll: simplify samsung_pll_lock_wait()

readl_relaxed_poll_timeout_atomic() has been updated in 2023 in
commit 7349a69cf312 ("iopoll: Do not use timekeeping in
read_poll_timeout_atomic()") to avoid usage of timekeeping APIs. It
also never used udelay() when no delay was given.

With the implementation avoiding timekeeping APIs, and with a caller
not passing a delay, the timeout argument simply becomes a loop
counter.

Therefore the code here can be simplified to unconditionally use
readl_relaxed_poll_timeout_atomic(). The difference being the last
argument, the timeout (loop counter). Simply adjust it to pass the
more generous counter in all cases.

This change also allows us to drop all code around the
pll_early_timeout variable as it is unused now.

Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>
Signed-off-by: André Draszik <andre.draszik@...aro.org>
---
Changes in v2:
- drop pll_early_timeout (Krzysztof)
- drop timekeeping.h
- collect tags
- Link to v1: https://lore.kernel.org/r/20251001-samsung-clk-pll-simplification-v1-1-d12def9e74b2@linaro.org
---
 drivers/clk/samsung/clk-pll.c | 41 ++++++++++-------------------------------
 1 file changed, 10 insertions(+), 31 deletions(-)

diff --git a/drivers/clk/samsung/clk-pll.c b/drivers/clk/samsung/clk-pll.c
index 7bea7be1d7e45c32f0b303ffa55ce9cde4a4f71d..0a8fc9649ae2975b1b19669fd5192bae984aa57b 100644
--- a/drivers/clk/samsung/clk-pll.c
+++ b/drivers/clk/samsung/clk-pll.c
@@ -11,14 +11,12 @@
 #include <linux/iopoll.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
-#include <linux/timekeeping.h>
 #include <linux/clk-provider.h>
 #include <linux/io.h>
 #include "clk.h"
 #include "clk-pll.h"
 
-#define PLL_TIMEOUT_US		20000U
-#define PLL_TIMEOUT_LOOPS	1000000U
+#define PLL_TIMEOUT_LOOPS	20000U
 
 struct samsung_clk_pll {
 	struct clk_hw		hw;
@@ -71,20 +69,11 @@ static int samsung_pll_determine_rate(struct clk_hw *hw,
 	return 0;
 }
 
-static bool pll_early_timeout = true;
-
-static int __init samsung_pll_disable_early_timeout(void)
-{
-	pll_early_timeout = false;
-	return 0;
-}
-arch_initcall(samsung_pll_disable_early_timeout);
-
 /* Wait until the PLL is locked */
 static int samsung_pll_lock_wait(struct samsung_clk_pll *pll,
 				 unsigned int reg_mask)
 {
-	int i, ret;
+	int ret;
 	u32 val;
 
 	/*
@@ -93,25 +82,15 @@ static int samsung_pll_lock_wait(struct samsung_clk_pll *pll,
 	 * initialized, another when the timekeeping is suspended. udelay() also
 	 * cannot be used when the clocksource is not running on arm64, since
 	 * the current timer is used as cycle counter. So a simple busy loop
-	 * is used here in that special cases. The limit of iterations has been
-	 * derived from experimental measurements of various PLLs on multiple
-	 * Exynos SoC variants. Single register read time was usually in range
-	 * 0.4...1.5 us, never less than 0.4 us.
+	 * is used here.
+	 * The limit of iterations has been derived from experimental
+	 * measurements of various PLLs on multiple Exynos SoC variants. Single
+	 * register read time was usually in range 0.4...1.5 us, never less than
+	 * 0.4 us.
 	 */
-	if (pll_early_timeout || timekeeping_suspended) {
-		i = PLL_TIMEOUT_LOOPS;
-		while (i-- > 0) {
-			if (readl_relaxed(pll->con_reg) & reg_mask)
-				return 0;
-
-			cpu_relax();
-		}
-		ret = -ETIMEDOUT;
-	} else {
-		ret = readl_relaxed_poll_timeout_atomic(pll->con_reg, val,
-					val & reg_mask, 0, PLL_TIMEOUT_US);
-	}
-
+	ret = readl_relaxed_poll_timeout_atomic(pll->con_reg, val,
+						val & reg_mask, 0,
+						PLL_TIMEOUT_LOOPS);
 	if (ret < 0)
 		pr_err("Could not lock PLL %s\n", clk_hw_get_name(&pll->hw));
 

---
base-commit: 2b763d4652393c90eaa771a5164502ec9dd965ae
change-id: 20251001-samsung-clk-pll-simplification-3e02f8912122

Best regards,
-- 
André Draszik <andre.draszik@...aro.org>