linux-kernel - Re: [RFC 06/19] devfreq: imx8m-ddrc: Add late system sleep PM ops

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Message-ID: <YaaENEqlQbW8W6PI@ryzen>
Date:   Tue, 30 Nov 2021 22:06:12 +0200
From:   Abel Vesa <abel.vesa@....com>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>
Cc:     Rob Herring <robh@...nel.org>, Dong Aisheng <aisheng.dong@....com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Georgi Djakov <djakov@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Ahmad Fatoum <a.fatoum@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linux-serial@...r.kernel.org, NXP Linux Team <linux-imx@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 06/19] devfreq: imx8m-ddrc: Add late system sleep PM ops

On 21-11-10 13:15:26, Martin Kepplinger wrote:
> Am Montag, dem 13.09.2021 um 20:38 +0300 schrieb Abel Vesa:
> > Seems that, in order to be able to resume from suspend, the dram rate
> > needs to be the highest one available. Therefore, add the late system
> > suspend/resume PM ops which set the highest rate on suspend and the
> > latest one used before suspending on resume.
> 
> Hi Abel, wouldn't this mean that s2idle / freeze would be kind of
> broken by this?
> 

Nope. Only the DDR rate needs to be raised at 800M before suspending.
Everything else stays the same.

> Does is make sense to test the lowest rate? How would I force that
> here? (just for testing)

You can try, but it will surely freeze. See [1] what you need to change
for testing.
> 
> Also, you could think about splitting this series up a bit and do this
> patch seperately onto mainline (before or after the other work).
> 

Well, I sent as RFC until now. Seems there are no big issues with the
approach. So I'll split the patches between subsystems on the next
iteration.

> thank you
>                           martin
> 
> 
> > 
> > Signed-off-by: Abel Vesa <abel.vesa@....com>
> > ---
> >  drivers/devfreq/imx8m-ddrc.c | 28 +++++++++++++++++++++++++++-
> >  1 file changed, 27 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/devfreq/imx8m-ddrc.c b/drivers/devfreq/imx8m-
> > ddrc.c
> > index f18a5c3c1c03..f39741b4a0b0 100644
> > --- a/drivers/devfreq/imx8m-ddrc.c
> > +++ b/drivers/devfreq/imx8m-ddrc.c
> > @@ -72,6 +72,8 @@ struct imx8m_ddrc {
> >         struct clk *dram_alt;
> >         struct clk *dram_apb;
> >  
> > +       unsigned long suspend_rate;
> > +       unsigned long resume_rate;
> >         int freq_count;
> >         struct imx8m_ddrc_freq freq_table[IMX8M_DDRC_MAX_FREQ_COUNT];
> >  };
> > @@ -271,6 +273,22 @@ static int imx8m_ddrc_target(struct device *dev,
> > unsigned long *freq, u32 flags)
> >         return ret;
> >  }
> >  
> > +static int imx8m_ddrc_suspend(struct device *dev)
> > +{
> > +       struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> > +
> > +       priv->resume_rate = clk_get_rate(priv->dram_core);
> > +
> > +       return imx8m_ddrc_target(dev, &priv->suspend_rate, 0);
> > +}
> > +
> > +static int imx8m_ddrc_resume(struct device *dev)
> > +{
> > +       struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> > +
> > +       return imx8m_ddrc_target(dev, &priv->resume_rate, 0);
> > +}
> > +
> >  static int imx8m_ddrc_get_cur_freq(struct device *dev, unsigned long
> > *freq)
> >  {
> >         struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> > @@ -324,6 +342,9 @@ static int imx8m_ddrc_init_freq_info(struct
> > device *dev)
> >  
> >                 if (dev_pm_opp_add(dev, freq->rate * 250000, 0))
> >                         return -ENODEV;
> > +
> > +               if (index ==  0)

[1] Change this line to:
		    if (index == 1)

It will select the 166935483 freq for suspending.

> > +                       priv->suspend_rate = freq->rate * 250000;
> >         }
> >  
> >         return 0;
> > @@ -399,11 +420,16 @@ static const struct of_device_id
> > imx8m_ddrc_of_match[] = {
> >  };
> >  MODULE_DEVICE_TABLE(of, imx8m_ddrc_of_match);
> >  
> > +static const struct dev_pm_ops imx8m_ddrc_pm_ops = {
> > +       SET_LATE_SYSTEM_SLEEP_PM_OPS(imx8m_ddrc_suspend,
> > imx8m_ddrc_resume)
> > +};
> > +
> >  static struct platform_driver imx8m_ddrc_platdrv = {
> >         .probe          = imx8m_ddrc_probe,
> >         .driver = {
> >                 .name   = "imx8m-ddrc-devfreq",
> > -               .of_match_table = imx8m_ddrc_of_match,
> > +               .pm = &imx8m_ddrc_pm_ops,
> > +               .of_match_table = of_match_ptr(imx8m_ddrc_of_match),
> >         },
> >  };
> >  module_platform_driver(imx8m_ddrc_platdrv);
> 
>