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

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Date:   Tue, 16 Apr 2019 16:24:16 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Chanwoo Choi <cw00.choi@...sung.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

16.04.2019 4:45, Chanwoo Choi пишет:
> Hi,
> 
> I add one minor comment (KHZ -> hz).

Hello Chanwoo,

Thank you very much for the review!

> 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

Indeed, good catch.

> 
>>  		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>

Okay, thanks.