linux-kernel - Re: [PATCH] clk: qcom: gfm-mux: use runtime pm while accessing registers

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Date:   Tue, 21 Mar 2023 11:46:10 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        agross@...nel.org, andersson@...nel.org
Cc:     konrad.dybcio@...aro.org, mturquette@...libre.com,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        stable@...r.kernel.org, Amit Pundir <amit.pundir@...aro.org>
Subject: Re: [PATCH] clk: qcom: gfm-mux: use runtime pm while accessing registers

Quoting Srinivas Kandagatla (2023-03-21 10:57:58)
> gfm mux driver does support runtime pm but we never use it while
> accessing registers. Looks like this driver was getting lucky and
> totally depending on other drivers to leave the clk on.
> 
> Fix this by doing runtime pm while accessing registers.
> 
> Fixes: a2d8f507803e ("clk: qcom: Add support to LPASS AUDIO_CC Glitch Free Mux clocks")
> Cc: stable@...r.kernel.org
> Reported-by: Amit Pundir <amit.pundir@...aro.org>

Is there a link to the report?

> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  drivers/clk/qcom/lpass-gfm-sm8250.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/qcom/lpass-gfm-sm8250.c b/drivers/clk/qcom/lpass-gfm-sm8250.c
> index 96f476f24eb2..bcf0ea534f7f 100644
> --- a/drivers/clk/qcom/lpass-gfm-sm8250.c
> +++ b/drivers/clk/qcom/lpass-gfm-sm8250.c
> @@ -38,14 +38,37 @@ struct clk_gfm {
>  static u8 clk_gfm_get_parent(struct clk_hw *hw)
>  {
>         struct clk_gfm *clk = to_clk_gfm(hw);
> +       int ret;
> +       u8 parent;
> +
> +       ret = pm_runtime_resume_and_get(clk->priv->dev);
> +       if (ret < 0 && ret != -EACCES) {
> +               dev_err_ratelimited(clk->priv->dev,
> +                                   "pm_runtime_resume_and_get failed in %s, ret %d\n",
> +                                   __func__, ret);
> +               return ret;
> +       }
> +
> +       parent = readl(clk->gfm_mux) & clk->mux_mask;
> +
> +       pm_runtime_mark_last_busy(clk->priv->dev);
>  
> -       return readl(clk->gfm_mux) & clk->mux_mask;
> +       return parent;
>  }
>  
>  static int clk_gfm_set_parent(struct clk_hw *hw, u8 index)
>  {
>         struct clk_gfm *clk = to_clk_gfm(hw);
>         unsigned int val;
> +       int ret;
> +
> +       ret = pm_runtime_resume_and_get(clk->priv->dev);

Doesn't the clk framework already do this? Why do we need to do it
again?

> +       if (ret < 0 && ret != -EACCES) {
> +               dev_err_ratelimited(clk->priv->dev,
> +                                   "pm_runtime_resume_and_get failed in %s, ret %d\n",
> +                                   __func__, ret);
> +               return ret;
> +       }
>  
>         val = readl(clk->gfm_mux);
>