[PATCH v12 0/6] cpufreq: use generic cpufreq drivers for exynos platforms

Kevin Hilman [off-list ref] writes:

Hi Thomas,

Thomas Abraham [off-list ref] writes:

quoted

Changes since v11:
- Rebased on top of git://linuxtv.org/snawrocki/samsung.git for-v3.19-exynos-clk

Thanks for rebasing/reposting.

quoted

This patch series removes the use of Exynos4210 and Exynos5250 specific cpufreq
drivers and enables the use of cpufreq-dt driver for these platforms. This
series also enables cpufreq support for Exynos5420 using arm_big_little cpufreq
driver.

This series is based on the following branch.
git://linuxtv.org/snawrocki/samsung.git for-v3.19-exynos-clk

This series depends on the following patch which can be picked from
git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc.git samsung/dt
e540920cf21c (ARM: dts: add CPU nodes for Exynos4 SoCs).

This patch series has been tested on Exynos4210/5250/5420 based boards.
Tomasz Figa had plans to take this in the Samsung clock tree for v3.19
(http://www.spinics.net/lists/linux-samsung-soc/msg37933.html).
Sylwester, could you consider to merge this in your tree?

I tested this on exynos5800-peach-pi, and noticed a few things.

First, since voltage scaling is not currently supported, the CPU cluster
regulators (vdd_arm, and vdd_kfc) have to be set at sufficietnly high
voltage to support all the OPPs, otherwise things will likely hang.  I
think you should include something like the patch below[1] in this
series as well.

Second, as with earlier versions of this series, I'm still seeing lots
of "wait_until_divider_stable: timeout in divider stablization" messages
coming out when running powertop.

And, I just found another issue:

On exynos5800-peach-pi, setting the cpufreq default governor to
performance at compile time (CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y)
makes the kernel boot hang when the cpufreq driver is initialized.

However, setting the compile-time default to the userspace governor, and
then setting the performance governor via sysfs after the boot finishes
seems to work fine.

Kevin