linux-kernel - Re: [PATCH] clk: qcom: clk-alpha-pll: Do not use random stack value for recalc rate

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Message-ID: <140e036792e7d7468130a47b0724132d.sboyd@kernel.org>
Date: Mon, 02 Dec 2024 21:08:38 -0800
From: Stephen Boyd <sboyd@...nel.org>
To: Bjorn Andersson <andersson@...nel.org>, Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Michael Turquette <mturquette@...libre.com>, linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH] clk: qcom: clk-alpha-pll: Do not use random stack value for recalc rate

Quoting Krzysztof Kozlowski (2024-11-27 01:36:23)
> If regmap_read() fails, random stack value was used in calculating new
> frequency in recalc_rate() callbacks.  Such failure is really not
> expected as these are all MMIO reads, however code should be here
> correct and bail out.  This also avoids possible warning on
> uninitialized value.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> ---
>  drivers/clk/qcom/clk-alpha-pll.c | 41 ++++++++++++++++++++++----------
>  1 file changed, 29 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
> index 5e9217ea3760..0cd937ab47d0 100644
> --- a/drivers/clk/qcom/clk-alpha-pll.c
> +++ b/drivers/clk/qcom/clk-alpha-pll.c
> @@ -682,9 +682,12 @@ clk_alpha_pll_recalc_rate(struct clk_hw *hw, unsigned long parent_rate)
>         struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
>         u32 alpha_width = pll_alpha_width(pll);
>  
> -       regmap_read(pll->clkr.regmap, PLL_L_VAL(pll), &l);
> +       if (regmap_read(pll->clkr.regmap, PLL_L_VAL(pll), &l))
> +               return 0;
> +
> +       if (regmap_read(pll->clkr.regmap, PLL_USER_CTL(pll), &ctl))
> +               return 0;
>  
> -       regmap_read(pll->clkr.regmap, PLL_USER_CTL(pll), &ctl);
>         if (ctl & PLL_ALPHA_EN) {
>                 regmap_read(pll->clkr.regmap, PLL_ALPHA_VAL(pll), &low);

What about 'low'?

>                 if (alpha_width > 32) {