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

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Date:   Tue, 21 Mar 2023 20:33:49 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Stephen Boyd <sboyd@...nel.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, stable@...r.kernel.org,
        Amit Pundir <amit.pundir@...aro.org>
Subject: Re: [PATCH] clk: qcom: gfm-mux: use runtime pm while accessing
 registers



On 21/03/2023 18:46, Stephen Boyd wrote:
> 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?

https://www.spinics.net/lists/stable/msg638380.html

> 
>> 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?

You are right, clk core already does do pm_runtime_resume_and_get for 
set_parent.

this looks redundant here.


so we need only need to add this for get_parent

--srini
> 
>> +       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);
>>