problems getting AMD C-70 APU working with powerd/cpufreq

[Anthony Jenkins]

Sorry for late responses (below).

On 10/21/2017 09:15, tech-lists wrote:
> On Wed, Oct 18, 2017 at 12:42:42PM +0100, tech-lists wrote:
>> On Tue, Oct 17, 2017 at 06:23:06PM -0400, Anthony Jenkins wrote:
>>> cpufreq(4) does not support AMD processor family 0x14 (20), which I
>>> believe your dmesg showed your processor to be.
>>
>> aha!
>>
>>> I had added support for controlling the frequency on some later AMD
>>> families last year, but the AMD documentation for the 0x14 family is
>>> pretty complicated for my tiny brain.  The other families control
>>> processor frequency with a single register, but AFACT you use P-states
>>> on family 0x14.  You can have up to 8 P-states, each of which specifies
>>> a power/frequency configuration.  If someone could point me to a
>>> reference for controlling the frequency for this family, I could submit
>>> something for review...no idea what Linux does for this family.
>>
>> Would it help if I were to get hardware output from booting temporarily
>> to linux mint?
>
> [thought I'd try it anyway]
>
> Linux info here:
> https://www.zyxst.net/txt/amd-c70-netbook/linux-dmesg-amdc70.txt
> https://www.zyxst.net/txt/amd-c70-netbook/linux-cpufreq-info-amdc70.txt
>
> cpufreq appears to be working on linux.
Linux' cpufreq looks vastly different from FreeBSD's, but I might be
able to borrow stuff from it.

> Because of this and that
> brightness control works, I've installed linux mint permanently. If you
> need me to, I can easily boot into freebsd to run tests; equally can run
> tests from linux. I'd prefer to run freebsd, but the inability to turn
> down screen brightness was a showstopper.
The following (git-based) patch /might/ fix your backlight issue:

http://www.qtchat.org/~ajenkins/20171025_radeon_backlight.patch

it should apply cleanly to recent FreeBSD kernel sources.  It works for
my HP Envy w/ Radeon GPU.  You'll need to rebuild the sys/dev/drm2 stuff
in the kernel, reinstall kernel and reboot (or just rebuild the drm2
modules if you're using those); you'll also need to load the acpi_video
module.  The keyboard backlight keys /should/ work then.  If not, post a
verbose dmesg log.

Anthony

> many thanks,