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Subject: Re: [PATCH v5 13/36] PM / devfreq: tegra30: Use MC timings for
 building OPP table
To:     Dmitry Osipenko <digetx@gmail.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Georgi Djakov <georgi.djakov@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Peter De Schrijver <pdeschrijver@nvidia.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Mikko Perttunen <cyndis@kapsi.fi>
Cc:     linux-tegra@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        devicetree@vger.kernel.org
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
Message-ID: <1b0d75fe-79af-70eb-8450-999a3bc72bac@samsung.com>
Date:   Fri, 14 Aug 2020 11:02:40 +0900
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Hi Dmitry,

I add the minor comment. Except of some comments, it looks good to me.

On 8/14/20 9:05 AM, Dmitry Osipenko wrote:
> The clk_round_rate() won't be usable for building OPP table once
> interconnect support will be added to the EMC driver because that CLK API
> function limits the rounded rate based on the clk rate that is imposed by
> active clk-users, and thus, the rounding won't work as expected if
> interconnect will set the minimum EMC clock rate before devfreq driver is
> loaded. The struct tegra_mc contains memory timings which could be used by
> the devfreq driver for building up OPP table instead of rounding clock
> rate, this patch implements this idea.
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/devfreq/tegra30-devfreq.c | 93 +++++++++++++++++++++----------
>  1 file changed, 65 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
> index 423dd35c95b3..6c2f56b34535 100644
> --- a/drivers/devfreq/tegra30-devfreq.c
> +++ b/drivers/devfreq/tegra30-devfreq.c
> @@ -19,6 +19,8 @@
>  #include <linux/reset.h>
>  #include <linux/workqueue.h>
>  
> +#include <soc/tegra/mc.h>
> +
>  #include "governor.h"
>  
>  #define ACTMON_GLB_STATUS					0x0
> @@ -153,6 +155,18 @@ struct tegra_devfreq_device {
>  	unsigned long target_freq;
>  };
>  
> +struct tegra_devfreq_soc_data {
> +	const char *mc_compatible;
> +};
> +
> +static const struct tegra_devfreq_soc_data tegra30_soc = {
> +	.mc_compatible = "nvidia,tegra30-mc",
> +};
> +
> +static const struct tegra_devfreq_soc_data tegra124_soc = {
> +	.mc_compatible = "nvidia,tegra124-mc",
> +};
> +
>  struct tegra_devfreq {
>  	struct devfreq		*devfreq;
>  
> @@ -771,15 +785,49 @@ static struct devfreq_governor tegra_devfreq_governor = {
>  	.interrupt_driven = true,
>  };
>  
> +static struct tegra_mc *tegra_get_memory_controller(const char *compatible)
> +{
> +	struct platform_device *pdev;
> +	struct device_node *np;
> +	struct tegra_mc *mc;
> +
> +	np = of_find_compatible_node(NULL, NULL, compatible);
> +	if (!np)
> +		return ERR_PTR(-ENOENT);
> +
> +	pdev = of_find_device_by_node(np);
> +	of_node_put(np);
> +	if (!pdev)
> +		return ERR_PTR(-ENODEV);
> +
> +	mc = platform_get_drvdata(pdev);
> +	if (!mc)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	return mc;
> +}
> +
>  static int tegra_devfreq_probe(struct platform_device *pdev)
>  {
> +	const struct tegra_devfreq_soc_data *soc_data;
>  	struct tegra_devfreq_device *dev;
>  	struct tegra_devfreq *tegra;
>  	struct devfreq *devfreq;
> +	struct tegra_mc *mc;
>  	unsigned int i;
> -	long rate;
>  	int err;
>  
> +	soc_data = of_device_get_match_data(&pdev->dev);

I think that better to check whether 'soc_data' is not NULL.


> +
> +	mc = tegra_get_memory_controller(soc_data->mc_compatible);
> +	if (IS_ERR(mc))
> +		return PTR_ERR(mc);

You better to add error log.

> +
> +	if (!mc->num_timings) {
> +		dev_info(&pdev->dev, "memory controller has no timings\n");
> +		return -ENODEV;
> +	}
> +
>  	tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
>  	if (!tegra)
>  		return -ENOMEM;
> @@ -825,6 +873,20 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  		return err;
>  	}
>  
> +	for (i = 0; i < mc->num_timings; i++) {
> +		/*
> +		 * Memory Controller timings are sorted in ascending clock
> +		 * rate order, so the last timing will be the max freq.
> +		 */
> +		tegra->max_freq = mc->timings[i].rate / KHZ;
> +
> +		err = dev_pm_opp_add(&pdev->dev, tegra->max_freq, 0);
> +		if (err) {
> +			dev_err(&pdev->dev, "Failed to add OPP: %d\n", err);
> +			goto remove_opps;
> +		}
> +	}
> +
>  	reset_control_assert(tegra->reset);
>  
>  	err = clk_prepare_enable(tegra->clock);
> @@ -836,37 +898,12 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  
>  	reset_control_deassert(tegra->reset);
>  
> -	rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);
> -	if (rate < 0) {
> -		dev_err(&pdev->dev, "Failed to round clock rate: %ld\n", rate);
> -		return rate;
> -	}
> -
> -	tegra->max_freq = rate / KHZ;
> -
>  	for (i = 0; i < ARRAY_SIZE(actmon_device_configs); i++) {
>  		dev = tegra->devices + i;
>  		dev->config = actmon_device_configs + i;
>  		dev->regs = tegra->regs + dev->config->offset;
>  	}
>  
> -	for (rate = 0; rate <= tegra->max_freq * KHZ; rate++) {
> -		rate = clk_round_rate(tegra->emc_clock, rate);
> -
> -		if (rate < 0) {
> -			dev_err(&pdev->dev,
> -				"Failed to round clock rate: %ld\n", rate);
> -			err = rate;
> -			goto remove_opps;
> -		}
> -
> -		err = dev_pm_opp_add(&pdev->dev, rate / KHZ, 0);
> -		if (err) {
> -			dev_err(&pdev->dev, "Failed to add OPP: %d\n", err);
> -			goto remove_opps;
> -		}
> -	}
> -
>  	platform_set_drvdata(pdev, tegra);
>  
>  	tegra->clk_rate_change_nb.notifier_call = tegra_actmon_clk_notify_cb;
> @@ -921,8 +958,8 @@ static int tegra_devfreq_remove(struct platform_device *pdev)
>  }
>  
>  static const struct of_device_id tegra_devfreq_of_match[] = {
> -	{ .compatible = "nvidia,tegra30-actmon" },
> -	{ .compatible = "nvidia,tegra124-actmon" },
> +	{ .compatible = "nvidia,tegra30-actmon",  .data = &tegra30_soc, },
> +	{ .compatible = "nvidia,tegra124-actmon", .data = &tegra124_soc, },
>  	{ },
>  };
>  
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics