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Subject: Re: [RFC 06/19] devfreq: imx8m-ddrc: Use the opps acquired from EL3
To:     Abel Vesa <abel.vesa@nxp.com>, Rob Herring <robh@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <kernel@pengutronix.de>,
        Lucas Stach <l.stach@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Georgi Djakov <djakov@kernel.org>,
        Dong Aisheng <aisheng.dong@nxp.com>,
        Peng Fan <peng.fan@nxp.com>,
        Martin Kepplinger <martink@posteo.de>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-clk@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc:     NXP Linux Team <linux-imx@nxp.com>
References: <1613750416-11901-1-git-send-email-abel.vesa@nxp.com>
 <1613750416-11901-7-git-send-email-abel.vesa@nxp.com>
From:   Chanwoo Choi <cwchoi00@gmail.com>
Message-ID: <62dd9f7d-f767-01ee-87eb-bd0553b53417@gmail.com>
Date:   Sat, 27 Feb 2021 00:12:24 +0900
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Hi,

On 21. 2. 20. 오전 1:00, Abel Vesa wrote:
> i.MX8M platforms get their dram OPPs from the EL3.
> We don't need to duplicate that in the kernel dram dts node.
> We should just trust the OPPs provided by the EL3.
> 
> Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
> ---
>   drivers/devfreq/imx8m-ddrc.c | 49 ++----------------------------------
>   1 file changed, 2 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/devfreq/imx8m-ddrc.c b/drivers/devfreq/imx8m-ddrc.c
> index 3a6c04ba4f2e..33de83acfd8b 100644
> --- a/drivers/devfreq/imx8m-ddrc.c
> +++ b/drivers/devfreq/imx8m-ddrc.c
> @@ -333,38 +333,9 @@ static int imx8m_ddrc_init_freq_info(struct device *dev)
>   		if (freq->dram_core_parent_index == 2 &&
>   				freq->dram_alt_parent_index == 0)
>   			return -ENODEV;
> -	}
> -
> -	return 0;
> -}
> -
> -static int imx8m_ddrc_check_opps(struct device *dev)
> -{
> -	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> -	struct imx8m_ddrc_freq *freq_info;
> -	struct dev_pm_opp *opp;
> -	unsigned long freq;
> -	int i, opp_count;
> -
> -	/* Enumerate DT OPPs and disable those not supported by firmware */
> -	opp_count = dev_pm_opp_get_opp_count(dev);
> -	if (opp_count < 0)
> -		return opp_count;
> -	for (i = 0, freq = 0; i < opp_count; ++i, ++freq) {
> -		opp = dev_pm_opp_find_freq_ceil(dev, &freq);
> -		if (IS_ERR(opp)) {
> -			dev_err(dev, "Failed enumerating OPPs: %ld\n",
> -				PTR_ERR(opp));
> -			return PTR_ERR(opp);
> -		}
> -		dev_pm_opp_put(opp);
>   
> -		freq_info = imx8m_ddrc_find_freq(priv, freq);
> -		if (!freq_info) {
> -			dev_info(dev, "Disable unsupported OPP %luHz %luMT/s\n",
> -					freq, DIV_ROUND_CLOSEST(freq, 250000));
> -			dev_pm_opp_disable(dev, freq);
> -		}
> +		if (dev_pm_opp_add(dev, freq->rate * 250000, 0))
> +			return -ENODEV;
>   	}
>   
>   	return 0;
> @@ -372,7 +343,6 @@ static int imx8m_ddrc_check_opps(struct device *dev)
>   
>   static void imx8m_ddrc_exit(struct device *dev)
>   {
> -	dev_pm_opp_of_remove_table(dev);
>   }
>   
>   static int imx8m_ddrc_probe(struct platform_device *pdev)
> @@ -419,16 +389,6 @@ static int imx8m_ddrc_probe(struct platform_device *pdev)
>   		return ret;
>   	}
>   
> -	ret = dev_pm_opp_of_add_table(dev);
> -	if (ret < 0) {
> -		dev_err(dev, "failed to get OPP table\n");
> -		return ret;
> -	}
> -
> -	ret = imx8m_ddrc_check_opps(dev);
> -	if (ret < 0)
> -		goto err;

In the devfreq_add_device(), if devfreq->profile->freq_table is NULL,
set_freq_table() function fill out the devfreq->profile->freq_table by 
using the OPP information.

After this patch, devfreq->profile.freq_table is NULL and there are no 
any OPP entries for this device, I think that this driver cannot add 
devfreq device without any frequency information. Is it working without 
any device frequency information?

> -
>   	priv->profile.polling_ms = 1000;
>   	priv->profile.target = imx8m_ddrc_target;
>   	priv->profile.get_dev_status = imx8m_ddrc_get_dev_status;
> @@ -441,13 +401,8 @@ static int imx8m_ddrc_probe(struct platform_device *pdev)
>   	if (IS_ERR(priv->devfreq)) {
>   		ret = PTR_ERR(priv->devfreq);
>   		dev_err(dev, "failed to add devfreq device: %d\n", ret);
> -		goto err;
>   	}
>   
> -	return 0;
> -
> -err:
> -	dev_pm_opp_of_remove_table(dev);
>   	return ret;
>   }
>   
>