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

[Martin Kepplinger]

Am Dienstag, dem 30.11.2021 um 22:06 +0200 schrieb Abel Vesa:
> 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.

well, for s2idle, linux stays running, so no calling out to atf (dram
retention...) is happening, so it'll stay at 800M *during* being
suspended.

I tested that by observing power consumption of the system - although
for now without the cpu-sleep state (via your workaround) due to
https://lore.kernel.org/linux-arm-kernel/6ca0bcabfa3b6643f9ab7e311cd8697df223c5cb.camel@puri.sm/


> 
> > 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.

thanks, that looks nicer than forcing 50M.

> > 
> > 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.

great, looking forward to it!

> 
> > thank you
> >                           martin
> > 
> > 
> > > 
> > > Signed-off-by: Abel Vesa <abel.vesa at nxp.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);
> > 
> >