Re: [PATCH V4 11/11] clk: imx: lpcg: add suspend/resume support

[Dong Aisheng <dongas86@gmail.com>]

On Sat, Sep 7, 2019 at 9:22 PM Stephen Boyd <sboyd@kernel.org> wrote:
>
> Quoting Dong Aisheng (2019-08-20 04:13:25)
> > diff --git a/drivers/clk/imx/clk-lpcg-scu.c b/drivers/clk/imx/clk-lpcg-scu.c
> > index 3c092a0..4df0818 100644
> > --- a/drivers/clk/imx/clk-lpcg-scu.c
> > +++ b/drivers/clk/imx/clk-lpcg-scu.c
> > @@ -33,6 +33,9 @@ struct clk_lpcg_scu {
> >         void __iomem *reg;
> >         u8 bit_idx;
> >         bool hw_gate;
> > +
> > +       /* for state save&restore */
> > +       u32 state;
> >  };
> >
> >  #define to_clk_lpcg_scu(_hw) container_of(_hw, struct clk_lpcg_scu, hw)
> > @@ -112,5 +115,35 @@ struct clk_hw *__imx_clk_lpcg_scu(struct device *dev, const char *name,
> >                 hw = ERR_PTR(ret);
> >         }
> >
> > +       if (dev)
> > +               dev_set_drvdata(dev, clk);
> > +
> >         return hw;
> >  }
> > +
> > +int __maybe_unused imx_clk_lpcg_scu_suspend(struct device *dev)
>
> static?
>
> > +{
> > +       struct clk_lpcg_scu *clk = dev_get_drvdata(dev);
> > +
> > +       clk->state = readl_relaxed(clk->reg);
> > +       dev_dbg(dev, "save lpcg state 0x%x\n", clk->state);
> > +
> > +       return 0;
> > +}
> > +
> > +int __maybe_unused imx_clk_lpcg_scu_resume(struct device *dev)
>
> static?
>

Will fix.

> > +{
> > +       struct clk_lpcg_scu *clk = dev_get_drvdata(dev);
> > +
> > +       /* FIXME: double write in case a failure */
>
> What does this mean? Sometimes writes don't work unless the CPU issues
> them twice?
>

Yes, it's a hardware timing issues.

Regards
Aisheng

> > +       writel(clk->state, clk->reg);
> > +       writel(clk->state, clk->reg);
> > +       dev_dbg(dev, "restore lpcg state 0x%x\n", clk->state);
> > +
> > +       return 0;
> > +}
> > +
> > +const struct dev_pm_ops imx_clk_lpcg_scu_pm_ops = {
> > +       SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(imx_clk_lpcg_scu_suspend,
> > +                                     imx_clk_lpcg_scu_resume)
> > +};