linux-kernel - Re: [For-STABLE] thermal/drivers/cpufreq_cooling: Fix wrong frequency converted from power

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Message-ID: <20200720121840.GB2984743@kroah.com>
Date:   Mon, 20 Jul 2020 14:18:40 +0200
From:   Greg KH <greg@...ah.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     stable@...r.kernel.org,
        Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Javi Merino <javi.merino@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Finley Xiao <finley.xiao@...k-chips.com>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [For-STABLE] thermal/drivers/cpufreq_cooling: Fix wrong
 frequency converted from power

On Wed, Jul 08, 2020 at 01:23:43PM +0530, Viresh Kumar wrote:
> From: Finley Xiao <finley.xiao@...k-chips.com>
> 
> commit 371a3bc79c11b707d7a1b7a2c938dc3cc042fffb upstream.
> 
> The function cpu_power_to_freq is used to find a frequency and set the
> cooling device to consume at most the power to be converted. For example,
> if the power to be converted is 80mW, and the em table is as follow.
> struct em_cap_state table[] = {
> 	/* KHz     mW */
> 	{ 1008000, 36, 0 },
> 	{ 1200000, 49, 0 },
> 	{ 1296000, 59, 0 },
> 	{ 1416000, 72, 0 },
> 	{ 1512000, 86, 0 },
> };
> The target frequency should be 1416000KHz, not 1512000KHz.
> 
> Fixes: 349d39dc5739 ("thermal: cpu_cooling: merge frequency and power tables")
> Cc: <stable@...r.kernel.org> # v4.13+
> Signed-off-by: Finley Xiao <finley.xiao@...k-chips.com>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> Reviewed-by: Amit Kucheria <amit.kucheria@...aro.org>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Link: https://lore.kernel.org/r/20200619090825.32747-1-finley.xiao@rock-chips.com
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> Hi Greg,
> 
> I am resending this as I got your emails of this failing on 4.14, 4.19
> and 5.4. This should be applied to all three of them.
> 
> @Finley: I hope I have done it correctly, please do check it as this
> required me to rewrite the code to adapt to previous kernels.
> 
>  drivers/thermal/cpu_cooling.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> index 908a8014cf76..1f4387a5ceae 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -280,11 +280,11 @@ static u32 cpu_power_to_freq(struct cpufreq_cooling_device *cpufreq_cdev,
>  	int i;
>  	struct freq_table *freq_table = cpufreq_cdev->freq_table;
>  
> -	for (i = 1; i <= cpufreq_cdev->max_level; i++)
> -		if (power > freq_table[i].power)
> +	for (i = 0; i < cpufreq_cdev->max_level; i++)
> +		if (power >= freq_table[i].power)
>  			break;
>  
> -	return freq_table[i - 1].frequency;
> +	return freq_table[i].frequency;
>  }
>  
>  /**
> -- 
> 2.25.0.rc1.19.g042ed3e048af
> 

Now queued up, thanks.

greg k-h