linux-kernel - Re: [PATCH v2 0/7] cpufreq support for Raspberry Pi

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Date:   Sat, 8 Jun 2019 12:43:18 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        linux-kernel@...r.kernel.org
Cc:     mbrugger@...e.de, viresh.kumar@...aro.org, rjw@...ysocki.net,
        sboyd@...nel.org, eric@...olt.net, f.fainelli@...il.com,
        bcm-kernel-feedback-list@...adcom.com, ptesarik@...e.com,
        linux-rpi-kernel@...ts.infradead.org, ssuloev@...altech.com,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        mturquette@...libre.com, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 0/7] cpufreq support for Raspberry Pi

Am 06.06.19 um 16:22 schrieb Nicolas Saenz Julienne:
> Hi all,
> this aims at adding cpufreq support to the Raspberry Pi family of
> boards.
>
> The series first factors out 'pllb' from clk-bcm2385 and creates a new
> clk driver that operates it over RPi's firmware interface[1]. We are
> forced to do so as the firmware 'owns' the pll and we're not allowed to
> change through the register interface directly as we might race with the
> over-temperature and under-voltage protections provided by the firmware.
>
> Next it creates a minimal cpufreq driver that populates the CPU's opp
> table, and registers cpufreq-dt. Which is needed as the firmware
> controls the max and min frequencies available.

Here some figures from the Raspberry Pi 3 B+ as before/after comparison:

Dhrystone Benchmark 2.1 A7 32 Bit

 600 MHz, w/o Turbo (1): 1216.11 VAX MIPS
1400 MHz, w/o Turbo (2): 2839.67 VAX MIPS
1400 MHz, w   Turbo (3): 2839.45 VAX MIPS

Whetstone Single Precision C Benchmark  vfpv4 32 Bit

 600 MHz, w/o Turbo: 454.565 MWIPS
1400 MHz, w/o Turbo: 1062.494 MWIPS
1400 MHz, w   Turbo: 1061.723 MWIPS

Power consumption (32 bit, without Ethernet) with load ( cat /dev/zero )

 600 MHz, w/o Turbo: 2.48 W
1400 MHz, w/o Turbo: 3.2 W
1400 MHz, w   Turbo: 3.15 W

Note 1: This is the maximum performance before enabling any cpufreq driver.

Note 2: This is the maximum performance after enabling V2 of the cpufreq
driver
http://lists.infradead.org/pipermail/linux-arm-kernel/2019-June/657768.html

Note 3: This is the maximum performance after enabling the initial
cpufreq driver
http://lists.infradead.org/pipermail/linux-rpi-kernel/2019-April/008634.html