linux-kernel - Re: [PATCH v2 3/5] clk: amlogic: Add handling for PLL lock failure

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Message-ID: <1jikfwzt5x.fsf@starbuckisacylon.baylibre.com>
Date: Thu, 30 Oct 2025 09:32:26 +0100
From: Jerome Brunet <jbrunet@...libre.com>
To: Chuan Liu via B4 Relay <devnull+chuan.liu.amlogic.com@...nel.org>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,  Michael Turquette
 <mturquette@...libre.com>,  Stephen Boyd <sboyd@...nel.org>,  Kevin Hilman
 <khilman@...libre.com>,  Martin Blumenstingl
 <martin.blumenstingl@...glemail.com>,  chuan.liu@...ogic.com,
  linux-amlogic@...ts.infradead.org,  linux-clk@...r.kernel.org,
  linux-arm-kernel@...ts.infradead.org,  linux-kernel@...r.kernel.org,
  da@...re.computer
Subject: Re: [PATCH v2 3/5] clk: amlogic: Add handling for PLL lock failure

On Thu 30 Oct 2025 at 13:24, Chuan Liu via B4 Relay <devnull+chuan.liu.amlogic.com@...nel.org> wrote:

> From: Chuan Liu <chuan.liu@...ogic.com>
>
> If the PLL fails to lock, it should be disabled, This makes the logic
> more complete, and also helps save unnecessary power consumption when
> the PLL is malfunctioning.
>
> Signed-off-by: Chuan Liu <chuan.liu@...ogic.com>
> ---
>  drivers/clk/meson/clk-pll.c | 41 +++++++++++++++++++++++------------------
>  1 file changed, 23 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/clk/meson/clk-pll.c b/drivers/clk/meson/clk-pll.c
> index f81ebf6cc981..6c794adb8ccd 100644
> --- a/drivers/clk/meson/clk-pll.c
> +++ b/drivers/clk/meson/clk-pll.c
> @@ -353,6 +353,23 @@ static int meson_clk_pcie_pll_enable(struct clk_hw *hw)
>  	return -EIO;
>  }
>  
> +static void meson_clk_pll_disable(struct clk_hw *hw)
> +{
> +	struct clk_regmap *clk = to_clk_regmap(hw);
> +	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
> +
> +	/* Put the pll is in reset */
> +	if (MESON_PARM_APPLICABLE(&pll->rst))
> +		meson_parm_write(clk->map, &pll->rst, 1);
> +
> +	/* Disable the pll */
> +	meson_parm_write(clk->map, &pll->en, 0);
> +
> +	/* Disable PLL internal self-adaption current module */
> +	if (MESON_PARM_APPLICABLE(&pll->current_en))
> +		meson_parm_write(clk->map, &pll->current_en, 0);
> +}
> +
>  static int meson_clk_pll_enable(struct clk_hw *hw)
>  {
>  	struct clk_regmap *clk = to_clk_regmap(hw);
> @@ -397,29 +414,17 @@ static int meson_clk_pll_enable(struct clk_hw *hw)
>  		meson_parm_write(clk->map, &pll->l_detect, 0);
>  	}
>  
> -	if (meson_clk_pll_wait_lock(hw))
> +	if (meson_clk_pll_wait_lock(hw)) {
> +		/* disable PLL when PLL lock failed. */
> +		meson_clk_pll_disable(hw);
> +		pr_warn("%s: PLL lock failed!!!\n", clk_hw_get_name(hw));
> +

This is something that's likely to spam, so pr_warn_once() (if you must warn)
and I don't think 3 "!" are necessary to convey the message.

>  		return -EIO;
> +	}
>  
>  	return 0;
>  }
>  
> -static void meson_clk_pll_disable(struct clk_hw *hw)
> -{
> -	struct clk_regmap *clk = to_clk_regmap(hw);
> -	struct meson_clk_pll_data *pll = meson_clk_pll_data(clk);
> -
> -	/* Put the pll is in reset */
> -	if (MESON_PARM_APPLICABLE(&pll->rst))
> -		meson_parm_write(clk->map, &pll->rst, 1);
> -
> -	/* Disable the pll */
> -	meson_parm_write(clk->map, &pll->en, 0);
> -
> -	/* Disable PLL internal self-adaption current module */
> -	if (MESON_PARM_APPLICABLE(&pll->current_en))
> -		meson_parm_write(clk->map, &pll->current_en, 0);
> -}
> -
>  static int meson_clk_pll_set_rate(struct clk_hw *hw, unsigned long rate,
>  				  unsigned long parent_rate)
>  {

-- 
Jerome