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Message-ID: <20200721115053.GD17778@duo.ucw.cz>
Date: Tue, 21 Jul 2020 13:50:53 +0200
From: Pavel Machek <pavel@...x.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
Finley Xiao <finley.xiao@...k-chips.com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Amit Kucheria <amit.kucheria@...aro.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH 4.19 123/133] thermal/drivers/cpufreq_cooling: Fix wrong
frequency converted from power
Hi!
> 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.
It is possible that table is always sorted in the opposite direction
in 4.19...
@@ -86,7 +72,7 @@ struct cpufreq_cooling_device {
- struct freq_table *freq_table; /* In descending order */
(This was changed by a4e893e802e6a807df2e2f3f660f7399bc7e104e).
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -278,11 +278,11 @@ static u32 cpu_power_to_freq(struct cpuf
> 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;
> }
In that case the patch makes some sense.
Best regards,
Pavel
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