Slow performance of Odroid XU4 - cpufreq-dt patch needed?

Slow performance of Odroid XU4 - cpufreq-dt patch needed?

[Vasco Steinmetz]

Hello,

I'm trying to get an Odroid XU4 to run a more recent (e.g. 4.4+) kernel
than the last semiofficial 4.2 port from hardkernel (which doesn't boot
here at all).

Currently (thanks to a lot of patches from you guys) the board boots
happily with a kernel build from linux-next.

Nonetheless the CPU performance is rather poor, though all 8 cores are
enabled (no b/l switcher).

It seems to me the Cortex A15s are running in their slowest performance
mode (that is: lowest clock).
I don't know a way to read the core clocks, as no cpufreq driver is working.
Tried that also with exynos_defconfig, but with the same effect.


My question therefore is:

Is Bartlomiej's cpufreq-dt patchset for exynos54xx (last update was
mid-December) necessary to obtain the full performance on the 5422?

Unfortunately I can't get that patchset to work with the linux-next from
within the last two weeks.
If there's an update I would volunteer to test it thoroughly (by
compiling Gentoo on it ;) on the XU4.


Another point:

The XU4's SD card controller supports UHS mode (tested by booting the
original ubuntu with an ancient 3.x kernel on the emmc flash and reading
from a UHS SD card), the current linux mainline kernel (4.4+) apparently
doesn't either detect or enable UHS mode. The maximum SD speed is around
20MB/s instead of the 90MB/s the card supports and was shown with the
test above.

Is there patch available (maybe some missing dt clock or flag to enable
UHS)?


Kind regards,
Vasco

Re: Slow performance of Odroid XU4 - cpufreq-dt patch needed?

[Ben Gamari]

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Vasco Steinmetz <linux@kyberraum.net> writes:

> Hello,
>
> I'm trying to get an Odroid XU4 to run a more recent (e.g. 4.4+) kernel
> than the last semiofficial 4.2 port from hardkernel (which doesn't boot
> here at all).
>
I also struggled to get my XU4 to perform to expectations with recent kernels.
Indeed it seems that the board boots to 800 MHz or so without cpufreq.
Recently I've been using this branch [1] (based on Bartlomiej's
cpufreq-v5 patchset) and this [2] configuration with reasonably good
results.

Cheers,

- Ben


[1] https://github.com/bgamari/linux/tree/odroid-xu3-cpufreq-v5
[2] http://home.smart-cactus.org/~ben/linux-xu4.config

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Re: Slow performance of Odroid XU4 - cpufreq-dt patch needed?

[Vasco Steinmetz]

Ben Gamari schrieb:

> I also struggled to get my XU4 to perform to expectations with recent kernels.
> Indeed it seems that the board boots to 800 MHz or so without cpufreq.
> Recently I've been using this branch [1] (based on Bartlomiej's
> cpufreq-v5 patchset) and this [2] configuration with reasonably good
> results.

Thanks!

Cheers,
Vasco

Re: Slow performance of Odroid XU4 - cpufreq-dt patch needed?

[Krzysztof Kozlowski]

2016-01-14 1:16 GMT+09:00 Vasco Steinmetz <linux@kyberraum.net>:
> Hello,
>
> I'm trying to get an Odroid XU4 to run a more recent (e.g. 4.4+) kernel
> than the last semiofficial 4.2 port from hardkernel (which doesn't boot
> here at all).
>
> Currently (thanks to a lot of patches from you guys) the board boots
> happily with a kernel build from linux-next.
>
> Nonetheless the CPU performance is rather poor, though all 8 cores are
> enabled (no b/l switcher).
>
> It seems to me the Cortex A15s are running in their slowest performance
> mode (that is: lowest clock).
> I don't know a way to read the core clocks, as no cpufreq driver is working.
> Tried that also with exynos_defconfig, but with the same effect.

Where there is no cpufreq driver, everything depends on the
bootloader. Usually the bootloader sets the initial value of clocks
and regulators. It shouldn't be the lowest value, though.

> Another point:
>
> The XU4's SD card controller supports UHS mode (tested by booting the
> original ubuntu with an ancient 3.x kernel on the emmc flash and reading
> from a UHS SD card), the current linux mainline kernel (4.4+) apparently
> doesn't either detect or enable UHS mode. The maximum SD speed is around
> 20MB/s instead of the 90MB/s the card supports and was shown with the
> test above.
>
> Is there patch available (maybe some missing dt clock or flag to enable
> UHS)?

There was a patch from Anand Moon ("ARM: dts: use vmmc-supply of
emmc/sd for exynos5422-odroidxu3") but it did not reach the level of
acceptance for merging. It would be nice to continue that work.

Best regards,
Krzysztof

Re: Slow performance of Odroid XU4 - cpufreq-dt patch needed?

[Vasco Steinmetz]

Hi Krzysztof,

> Where there is no cpufreq driver, everything depends on the
> bootloader. Usually the bootloader sets the initial value of clocks
> and regulators. It shouldn't be the lowest value, though.

Right. The u-bloat in use is the pretty old one provided by hk (modified
u-boot-2012 IIRC), so that may explain unsuitable initial clock values.
Compiled a recent u-boot-2015.10 and also one from trunk, but it's image
size exceeds the hardcoded offsets within the signed firmware bootloader
from hk required to load u-boot.
Had also no success with another hk firmware bootloader I found which
could boot >500K u-boot images. It's a mess on this board (compared to
panda/beagle[bone]s).

Since I haven't got a 1.8v ttl uart cable with that rare connector,
debugging/analyzing bootloader or early kernel issues such as cpu init
or modifying the kconfig is pretty hard.

> There was a patch from Anand Moon ("ARM: dts: use vmmc-supply of
> emmc/sd for exynos5422-odroidxu3") but it did not reach the level of
> acceptance for merging. It would be nice to continue that work.

I saw that and hoped he'd repost an improved version based on your
comments. I'm new to this list so I will not try to bother you by
submitting patches (yet ;-).


Cheers,
Vasco