linux-kernel - Re: [PATCH v2 01/19] PM / devfreq: tegra: Fix kHz to Hz conversion

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Date:   Tue, 16 Apr 2019 10:45:55 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 01/19] PM / devfreq: tegra: Fix kHz to Hz conversion

Hi,

I add one minor comment (KHZ -> hz).

On 19. 4. 15. 오후 11:54, Dmitry Osipenko wrote:
> The kHz to Hz is incorrectly converted in a few places in the code,
> this results in a wrong frequency being calculated because devfreq core
> uses OPP frequencies that are given in Hz to clamp the rate, while
> tegra-devfreq gives to the core value in kHz and then it also expects to
> receive value in kHz from the core. In a result memory freq is always set
> to a value which is close to ULONG_MAX because of the bug. Hence the EMC
> frequency is always capped to the maximum and the driver doesn't do
> anything useful. This patch was tested on Tegra30 and Tegra124 SoC's, EMC
> frequency scaling works properly now.
> 
> Cc: <stable@...r.kernel.org> # 4.14+
> Tested-by: Steev Klimaszewski <steev@...i.org>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/devfreq/tegra-devfreq.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index c89ba7b834ff..02905978abe1 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -486,9 +486,9 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
>  {
>  	struct tegra_devfreq *tegra = dev_get_drvdata(dev);
>  	struct dev_pm_opp *opp;
> -	unsigned long rate = *freq * KHZ;
> +	unsigned long rate;
>  
> -	opp = devfreq_recommended_opp(dev, &rate, flags);
> +	opp = devfreq_recommended_opp(dev, freq, flags);
>  	if (IS_ERR(opp)) {
>  		dev_err(dev, "Failed to find opp for %lu KHz\n", *freq);

Need to change it as following:
- KHz -> Hz


>  		return PTR_ERR(opp);
> @@ -499,8 +499,6 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
>  	clk_set_min_rate(tegra->emc_clock, rate);
>  	clk_set_rate(tegra->emc_clock, 0);
>  
> -	*freq = rate;
> -
>  	return 0;
>  }
>  
> @@ -510,7 +508,7 @@ static int tegra_devfreq_get_dev_status(struct device *dev,
>  	struct tegra_devfreq *tegra = dev_get_drvdata(dev);
>  	struct tegra_devfreq_device *actmon_dev;
>  
> -	stat->current_frequency = tegra->cur_freq;
> +	stat->current_frequency = tegra->cur_freq * KHZ;
>  
>  	/* To be used by the tegra governor */
>  	stat->private_data = tegra;
> @@ -565,7 +563,7 @@ static int tegra_governor_get_target(struct devfreq *devfreq,
>  		target_freq = max(target_freq, dev->target_freq);
>  	}
>  
> -	*freq = target_freq;
> +	*freq = target_freq * KHZ;
>  
>  	return 0;
>  }
> 

It looks good to me if modify it in accordance with my comment.
Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

Regards,
Chanwoo Choi



-- 
Best Regards,
Chanwoo Choi
Samsung Electronics