linux-kernel - Re: [PATCH v4 08/24] PM / devfreq: tegra30: Move clk-notifier's registration to governor's start

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Message-ID: <17d965c5-4114-4143-30c9-54cd88f9eff3@samsung.com>
Date:   Tue, 16 Jul 2019 21:11:43 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:     linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 08/24] PM / devfreq: tegra30: Move clk-notifier's
 registration to governor's start

Hi Dmitiry,

On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote:
> There is no point in receiving of the notifications while governor is
> stopped, let's keep them disabled like we do for the CPU freq-change
> notifications. This also fixes a potential use-after-free bug if
> notification happens after device's removal.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/devfreq/tegra30-devfreq.c | 33 ++++++++++++++++++-------------
>  1 file changed, 19 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
> index 48a799fa5f63..d5d04c25023b 100644
> --- a/drivers/devfreq/tegra30-devfreq.c
> +++ b/drivers/devfreq/tegra30-devfreq.c
> @@ -576,6 +576,19 @@ static int tegra_actmon_start(struct tegra_devfreq *tegra)
>  	actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
>  		      ACTMON_GLB_PERIOD_CTRL);
>  
> +	/*
> +	 * CLK notifications are needed in order to reconfigure the upper
> +	 * consecutive watermark in accordance to the actual clock rate
> +	 * to avoid unnecessary upper interrupts.
> +	 */
> +	err = clk_notifier_register(tegra->emc_clock,
> +				    &tegra->clk_rate_change_nb);
> +	if (err) {
> +		dev_err(tegra->devfreq->dev.parent,
> +			"Failed to register rate change notifier\n");
> +		return err;
> +	}
> +
>  	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
>  		tegra_actmon_configure_device(tegra, &tegra->devices[i]);
>  
> @@ -602,6 +615,8 @@ static int tegra_actmon_start(struct tegra_devfreq *tegra)
>  	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
>  		tegra_actmon_stop_device(&tegra->devices[i]);
>  
> +	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
> +
>  	return err;
>  }
>  
> @@ -618,6 +633,8 @@ static void tegra_actmon_stop(struct tegra_devfreq *tegra)
>  
>  	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
>  		tegra_actmon_stop_device(&tegra->devices[i]);
> +
> +	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
>  }
>  
>  static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
> @@ -862,22 +879,14 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, tegra);
>  
> +	tegra->clk_rate_change_nb.notifier_call = tegra_actmon_clk_notify_cb;
>  	tegra->cpu_rate_change_nb.notifier_call = tegra_actmon_cpu_notify_cb;
>  	INIT_WORK(&tegra->update_work, tegra_actmon_delayed_update);
>  
> -	tegra->clk_rate_change_nb.notifier_call = tegra_actmon_clk_notify_cb;
> -	err = clk_notifier_register(tegra->emc_clock,
> -				    &tegra->clk_rate_change_nb);
> -	if (err) {
> -		dev_err(&pdev->dev,
> -			"Failed to register rate change notifier\n");
> -		goto remove_opps;
> -	}
> -
>  	err = devfreq_add_governor(&tegra_devfreq_governor);
>  	if (err) {
>  		dev_err(&pdev->dev, "Failed to add governor: %d\n", err);
> -		goto unreg_notifier;
> +		goto remove_opps;
>  	}
>  
>  	tegra_devfreq_profile.initial_freq = clk_get_rate(tegra->emc_clock);
> @@ -893,9 +902,6 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>  remove_governor:
>  	devfreq_remove_governor(&tegra_devfreq_governor);
>  
> -unreg_notifier:
> -	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
> -
>  remove_opps:
>  	dev_pm_opp_remove_all_dynamic(&pdev->dev);
>  
> @@ -912,7 +918,6 @@ static int tegra_devfreq_remove(struct platform_device *pdev)
>  	devfreq_remove_device(tegra->devfreq);
>  	devfreq_remove_governor(&tegra_devfreq_governor);
>  
> -	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
>  	dev_pm_opp_remove_all_dynamic(&pdev->dev);
>  
>  	reset_control_reset(tegra->reset);
> 

Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics