need guidance re amdgpu i2c

[Deucher, Alexander]

From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf Of Sanford Rockowitz
Sent: Tuesday, September 13, 2016 6:47 AM
To: amd-gfx at lists.freedesktop.org
Subject: need guidance re amdgpu i2c

First, apologies in advance if this is not the most appropriate list for my questions.  Redirection appreciated.

I am the author of ddctool<www.ddctool.com>, a utility to manipulate monitor settings using DDC/CI over I2C.

My understanding is that amdgpu provides /dev/i2c-* devices in the usual way, so that ddctool should just work without changes.  But of course this needs to be tested.

In this regard I have a number of questions and a request.

Does the i2c interface depend in some way on whether one is running the AMDGPU-PRO driver?

No, although the PRO driver uses a newer display stack which is not upstream yet so there may be subtle differences.

The most current AMD card that I own in a R9 280, which is a first generation GCN device.   Phoronix suggests that first generation GCN support is in the works.  Will this be soon?   If not, would the current development code for amdgpu be sufficient for me to test the i2c support?   If so, what would I have to do to build and install it?

Both radeon and amdgpu support the same i2c interfaces.  It doesn’t matter which driver you use.  The current SI support in amdgpu supports i2c.

Or should I just plunk down a few dollars for a relatively inexpensive R7 260, which I understand is supported by the current amdgpu?

Up to you.

Alternatively, if someone running the amdgpu driver would be willing to install and test ddctool on their system I'd be most appreciative.  The git repository is here: https://github.com/rockowitz/ddctool, and there's extensive documentation on the website, www.ddctool.com<http://www.ddctool.com>.

A couple of command line options of note:

  "--stats" reports extensive performance statistics, including counts of i2c retries required
  "--ddc"  reports DDC protocol data errors

If ddctool installs but does not seem to be working, command "ddctool environment" may provide some clues.

Finally, the "ddctool interrogate" command fully exercises ddctool and probes the i2c environment.  Depending on permissions, running it as root may provide additional detail.  If you can capture the output and send it to me that would be most helpful.

Thanks in advance,
Sanford Rockowitz
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