am335x smartreflex driver for recent kernels

Mårten

Hi!

I can't seem to get smartreflex working on a custom am335x based board with the 3.12 kernel from the latest SDK. It worked in the previous SDKs, which was based on kernel 3.2. Investigating it further it seems that am335x used a special smartreflex driver, called am335x_smartreflex.c which exists as a patch in the previous SDKs. But it seems to be missing in the latest SDK.
It says in a comment in the patch that work is being conducted in pushing the driver upstreams. But I see no signs of the driver in the ti kernel. Furthermore I found this somewhat cryptic message in the kernel release notes from the latest SDK, 07.00.00,

B-02423 AVS missing from integration tree

So what is TI's plan regarding smartreflex in am335x? Are you planning to maintain the driver and make it work on newer kernels or are you going to drop smartreflex support in am335x? Or am I missing something? AFAIK the smartreflex drivers already in the kernel tree doesnt work on am335x.

Regards,

Mårten

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi Marten,

Smartreflex is included in SDK 7.0. Check this wiki: http://processors.wiki.ti.com/index.php/Linux_Core_Power_Management_User%27s_Guide

0 Mårten over 10 years ago in reply to Biser Gatchev-XID

Prodigy 60 points

The wiki only says

Smartreflex

In other words Adaptive Voltage Scaling(AVS) is an active PM Technique and is based on the silicon type. Strong or weak devices. Hot devices are devices which can run at a particular frequency at a voltage lesser than the nominal voltage. Weak ones require higher voltage. There are various classes of AVS.

Nothing about how to use it or whether it is supported at all. In kernel 3.2 you could get debug information from /debug/smartreflex after mounting debugfs, but no such directory is present under 3.12. So how can you see whether smartreflex is working?

0 Biser Gatchev-XID over 10 years ago in reply to Mårten

TI__Guru**** 393215 points

Here is an quote from a presentation:

• View all available governors:

root@am335x-evm# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors

ondemand userspace performance conservative powersave

• View current governor:

root@am335x-evm # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

ondemand

• View and Change Frequency (OPP):

– First, set cpufreq governor to userspace

– View current frequency:

root@am335x-evm# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

720000

– View current voltage:

root@am335x-evm# cat /sys/class/regulator/regulator.3/microvolts

1262500

– View Supported OPPs:

root@am335x-evm# cat

/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

275000 500000 600000 720000

– Change Frequency to 500MHz:

root@am335x-evm# echo 500000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

0 Mårten over 10 years ago in reply to Biser Gatchev-XID

Prodigy 60 points

What you are showing me is DVFS, Dynamic Voltage and Frequency Scaling. That works.

What I am talking about is smartreflex, or AVS, Adaptive Voltage Scaling, which can modify the nominal voltages for each OPP, based on the properties of the silicon of the actual device.

0 Biser Gatchev-XID over 10 years ago in reply to Mårten

TI__Guru**** 393215 points

Here is the whole document: 0815.sitara_boot_camp_am335x_pm_sw_training.pdf

0 Mårten over 10 years ago in reply to Biser Gatchev-XID

Prodigy 60 points

Interesting document, but alas, it does not say anything about SmartReflex or AVS.

0 Mårten over 10 years ago in reply to Mårten

Prodigy 60 points

Found another discussion. Conclusion: SDK 7.0 is missing smartreflex support. From

http://e2e.ti.com/support/arm/sitara_arm/f/791/p/348157/1242718.aspx#1242718

Processors

Processors forum

am335x smartreflex driver for recent kernels

Smartreflex