linux-kernel - Re: [PATCH v2] clk: qcom: lpasscc: Re-configure the PLL in case lost

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Date:   Wed, 14 Oct 2020 14:13:54 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Taniya Das <tdas@...eaurora.org>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        David Brown <david.brown@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-soc@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] clk: qcom: lpasscc: Re-configure the PLL in case lost

Hi,

On Wed, Oct 14, 2020 at 10:21 AM Taniya Das <tdas@...eaurora.org> wrote:
>
> Thanks Doug for the patch.
>
> On 10/14/2020 9:28 PM, Douglas Anderson wrote:
> > From: Taniya Das <tdas@...eaurora.org>
> >
> > In the case where the PLL configuration is lost, then the pm runtime
> > resume will reconfigure before usage.
> >
> > Fixes: edab812d802d ("clk: qcom: lpass: Add support for LPASS clock controller for SC7180")
> > Signed-off-by: Taniya Das <tdas@...eaurora.org>
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > ---
> > I took the liberty of fixing my own nits that I had with Taniya's
> > patch, AKA:
> >
> > https://lore.kernel.org/r/1602614008-2421-2-git-send-email-tdas@codeaurora.org
> >
> > Changes in v2:
> > - Don't needlessly have a 2nd copy of dev_pm_ops and jam it in.
> > - Check the return value of pm_clk_resume()
> > - l_val should be unsigned int.
> >
> >   drivers/clk/qcom/lpasscorecc-sc7180.c | 23 ++++++++++++++++++++++-
> >   1 file changed, 22 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/clk/qcom/lpasscorecc-sc7180.c b/drivers/clk/qcom/lpasscorecc-sc7180.c
> > index 228d08f5d26f..ee23eb5b9bf2 100644
> > --- a/drivers/clk/qcom/lpasscorecc-sc7180.c
> > +++ b/drivers/clk/qcom/lpasscorecc-sc7180.c
> > @@ -356,6 +356,25 @@ static const struct qcom_cc_desc lpass_audio_hm_sc7180_desc = {
> >       .num_gdscs = ARRAY_SIZE(lpass_audio_hm_sc7180_gdscs),
> >   };
> >
> > +static int lpass_core_cc_pm_clk_resume(struct device *dev)
> > +{
> > +     struct regmap *regmap = dev_get_drvdata(dev);
> > +     unsigned int l_val;
> > +     int ret;
> > +
> > +     ret = pm_clk_resume(dev);
> > +     if (ret)
> > +             return ret;
> > +
> > +     /* Read PLL_L_VAL */
> > +     regmap_read(regmap, 0x1004, &l_val);
> > +     if (!l_val)
> > +             clk_fabia_pll_configure(&lpass_lpaaudio_dig_pll, regmap,
> > +                             &lpass_lpaaudio_dig_pll_config);
> > +
> > +     return 0;
> > +}
> > +
> >   static int lpass_core_cc_sc7180_probe(struct platform_device *pdev)
> >   {
> >       const struct qcom_cc_desc *desc;
> > @@ -373,6 +392,8 @@ static int lpass_core_cc_sc7180_probe(struct platform_device *pdev)
> >       if (IS_ERR(regmap))
> >               return PTR_ERR(regmap);
> >
> > +     dev_set_drvdata(&pdev->dev, regmap);
> > +
> >       /*
> >        * Keep the CLK always-ON
> >        * LPASS_AUDIO_CORE_SYSNOC_SWAY_CORE_CLK
> > @@ -449,7 +470,7 @@ static int lpass_core_sc7180_probe(struct platform_device *pdev)
> >   }
> >
> >   static const struct dev_pm_ops lpass_core_cc_pm_ops = {
> > -     SET_RUNTIME_PM_OPS(pm_clk_suspend, pm_clk_resume, NULL)
> > +     SET_RUNTIME_PM_OPS(pm_clk_suspend, lpass_core_cc_pm_clk_resume, NULL)
>
> There are two devices and "lpass_hm_core" and the PLL is not part of the
> HM_CORE, thus was the reason to separate out the pm_ops.

Oh, that's really weird / unexpected.  I've tried to disentangle this
in a v3 patch series so I'd be curious to see what people think.
Though it's probably fine to jam the "pm" value like your v1 did I
think it violates the "principle of least surprise" a bit.

-Doug