linux-kernel - Re: [PATCH 1/3] PM / OPP: Add support for descending order for cpufreq table

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Date:	Fri, 9 May 2014 04:59:28 -0700
From:	jonghwan Choi <jhbird.choi@...il.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Jonghwan Choi <jhbird.choi@...sung.com>,
	Nishanth Menon <nm@...com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>,
	Amit Daniel Kachhap <amit.daniel@...sung.com>
Subject: Re: [PATCH 1/3] PM / OPP: Add support for descending order for
 cpufreq table

On Thu, May 8, 2014 at 11:00 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:

> Why? So, as far as I got it your dividers are nothing but 0,1,2...
> i.e.
> Freqs: 400  500  600  700  800
> div:      4      3      2      1      0
>
> right? That's what you are doing in exynos5440. So just add this in your
> probe after doing: dev_pm_opp_init_cpufreq_table
>
> for(i = 0; all-available-freqs; i++)
>     dvfs_info->freq_table[i].driver_data = dvfs_info->freq_count - i;
>
> And this will work with changes in dts files.

I am sorry
I couldn’t provide detailed information about this suggestion.
This suggestion is not for exynos5440. This is for exynos4210,
exynos4x12 and exynos5250.
(But this can be applied to exynos5440 also)
I want to make exynos cpufreq driver simple.
There are exynos-cpufreq.c, exynos4210-cpufreq.c exynos4x12-cpufreq.
exynos5250-cpufreq.c for exynos soc.
And exynos4210-cpufreq.c, exynos4x12 and exynos5250-cpufreq. c has a
clk divider table for each frequency.

example) exynos4210-cpufreq.c
static struct apll_freq apll_freq_4210[] = {
        /*
         * values:
         * freq
         * clock divider for CORE, COREM0, COREM1, PERIPH, ATB,
PCLK_DBG, APLL, RESERVED
         * clock divider for COPY, HPM, RESERVED
         * PLL M, P, S
         */
        APLL_FREQ(1200, 0, 3, 7, 3, 4, 1, 7, 0, 5, 0, 0, 150, 3, 1),
        APLL_FREQ(1000, 0, 3, 7, 3, 4, 1, 7, 0, 4, 0, 0, 250, 6, 1),
        APLL_FREQ(800,  0, 3, 7, 3, 3, 1, 7, 0, 3, 0, 0, 200, 6, 1),
        APLL_FREQ(500,  0, 3, 7, 3, 3, 1, 7, 0, 3, 0, 0, 250, 6, 2),
        APLL_FREQ(200,  0, 1, 3, 1, 3, 1, 0, 0, 3, 0, 0, 200, 6, 3),
};

If we can pass this clk divider value to exynos cpufreq driver through
DT, we can remove most of exynosxxxx-cpufreq.c files/codes. And when
new frequency is added/removed or new soc is released, for supporting
dvfs we have only to describe frequency, voltage and divider value in
dts file.

Thanks

Best Regards.
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