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

[Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>]

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@xxxxxxxxxxxxxxx
> > Reported-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
>
> Is there a link to the report?

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

> > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> > ---
> >   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);