Re: [PATCH 3/3] drm/i915: rc6 in sysfs

[Ben Widawsky <ben@bwidawsk.net>]

On Sun, 25 Mar 2012 14:15:56 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Sat, Mar 24, 2012 at 07:09:46PM -0700, Ben Widawsky wrote:
> > Merge rc6 information into the power group for our device. Until
> > now the i915 driver has not had any sysfs entries (aside from the
> > connector stuff enabled by libdrm). Since it seems like we're
> > likely to have more in the future I created a new file for sysfs
> > stubs, as well as the rc6 sysfs functions which don't really belong
> > elsewhere (perhaps i915_suspend, but most of the stuff is in
> > intel_display,c).
> > 
> > displays #ms GPU has been in rc6 since boot:
> > cat /sys/class/drm/card0/power/rc6
> > 
> > displays #ms GPU has been in deep rc6 since boot:
> > cat /sys/class/drm/card0/power/rc6p
> > 
> > displays #ms GPU has been in deepest rc6 since boot:
> > cat /sys/class/drm/card0/power/rc6pp
> > 
> > Important note: I've seen on SNB that even when RC6 is *not*
> > enabled the rc6 register seems to have a random value in it. I
> > cannot explain a reason for this. Those writing tools that utilize
> > this value need to be careful and probably want to scrutinize the
> > value very carefully.
> > 
> > Please see intel-gpu-tools patches for sample code.
> > 
> > CC: Arjan van de Ven <arjan@linux.intel.com>
> > Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> 
> I like this (with the cleanups you've mentioned). While you dig
> around in sysfs, can I volunteer you to add another patch to create
> an official interface for i915_max_freq? Maybe call it
> max_gpu_freq_MHz (if MHz is an acceptable unit for sysfs files). We
> have a bug report which might get partially happy with this (there
> seem to be other issues):
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=41392a
> 
> Cheers, Daniel
> 

Yes. From looking at cpureq, it seems MHz is not standard. Simply
writing the frequency as a number in the [m|b]illions is the way to go.

I'll get on this once I get an ack from you that you pick up the later
versions of my sysfs stuff.