linux-kernel - [PATCH v3 4/4] clk: amlogic: Optimize PLL enable timing

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Message-Id: <20251031-optimize_pll_driver-v3-4-92f3b2f36a83@amlogic.com>
Date: Fri, 31 Oct 2025 16:10:11 +0800
From: Chuan Liu via B4 Relay <devnull+chuan.liu.amlogic.com@...nel.org>
To: Neil Armstrong <neil.armstrong@...aro.org>, 
 Jerome Brunet <jbrunet@...libre.com>, 
 Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Kevin Hilman <khilman@...libre.com>, 
 Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc: linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Chuan Liu <chuan.liu@...ogic.com>
Subject: [PATCH v3 4/4] clk: amlogic: Optimize PLL enable timing

From: Chuan Liu <chuan.liu@...ogic.com>

l_detect controls the enablement of the PLL lock detection module.
It should remain disabled while the internal PLL circuits are
reaching a steady state; otherwise, the lock signal may be falsely
triggered high.

A 20 us delay has been added before enabling the PLL, so there’s no
need for an additional 10 us delay before enabling current_en.

Currently, only A1 supports both l_detect and current_en, so this
patch will only affect A1.

Signed-off-by: Chuan Liu <chuan.liu@...ogic.com>
---
 drivers/clk/meson/clk-pll.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/meson/clk-pll.c b/drivers/clk/meson/clk-pll.c
index cdb39a723bd0..c9b941adf688 100644
--- a/drivers/clk/meson/clk-pll.c
+++ b/drivers/clk/meson/clk-pll.c
@@ -383,6 +383,10 @@ static int meson_clk_pll_enable(struct clk_hw *hw)
 	if (MESON_PARM_APPLICABLE(&pll->rst))
 		meson_parm_write(clk->map, &pll->rst, 1);
 
+	/* Disable the PLL lock-detect module */
+	if (MESON_PARM_APPLICABLE(&pll->l_detect))
+		meson_parm_write(clk->map, &pll->l_detect, 1);
+
 	/* Enable the pll */
 	meson_parm_write(clk->map, &pll->en, 1);
 
@@ -401,20 +405,18 @@ static int meson_clk_pll_enable(struct clk_hw *hw)
 	 * Compared with the previous SoCs, self-adaption current module
 	 * is newly added for A1, keep the new power-on sequence to enable the
 	 * PLL. The sequence is:
-	 * 1. enable the pll, delay for 10us
+	 * 1. enable the pll, delay for 20us
 	 * 2. enable the pll self-adaption current module, delay for 40us
 	 * 3. enable the lock detect module
 	 */
 	if (MESON_PARM_APPLICABLE(&pll->current_en)) {
-		udelay(10);
 		meson_parm_write(clk->map, &pll->current_en, 1);
 		udelay(40);
 	}
 
-	if (MESON_PARM_APPLICABLE(&pll->l_detect)) {
-		meson_parm_write(clk->map, &pll->l_detect, 1);
+	/* Enable the lock-detect module */
+	if (MESON_PARM_APPLICABLE(&pll->l_detect))
 		meson_parm_write(clk->map, &pll->l_detect, 0);
-	}
 
 	if (meson_clk_pll_wait_lock(hw)) {
 		/* disable PLL when PLL lock failed. */

-- 
2.42.0