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Subject: Re: [RFC 06/19] devfreq: imx8m-ddrc: Add late system sleep PM ops
From:   Martin Kepplinger <martin.kepplinger@puri.sm>
To:     Abel Vesa <abel.vesa@nxp.com>, Rob Herring <robh@kernel.org>,
        Dong Aisheng <aisheng.dong@nxp.com>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        "catalin.marinas@arm.com" <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Georgi Djakov <djakov@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc:     Pengutronix Kernel Team <kernel@pengutronix.de>,
        linux-serial@vger.kernel.org, NXP Linux Team <linux-imx@nxp.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        devicetree@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Date:   Wed, 10 Nov 2021 13:15:26 +0100
In-Reply-To: <1631554694-9599-7-git-send-email-abel.vesa@nxp.com>
References: <1631554694-9599-1-git-send-email-abel.vesa@nxp.com>
         <1631554694-9599-7-git-send-email-abel.vesa@nxp.com>
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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?

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

thank you
                          martin


> 
> Signed-off-by: Abel Vesa <abel.vesa@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)
> +                       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);