[Intel-gfx] [PATCH v4] drm/i915: rc6 in sysfs

[Chris Wilson]

On Tue, 10 Apr 2012 21:17:01 -0700, Ben Widawsky <ben at bwidawsk.net> 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 drm core). 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 rc6 modes enabled (as a hex mask):
> cat /sys/class/drm/card0/power/rc6_enable
> 
> displays #ms GPU has been in rc6 since boot:
> cat /sys/class/drm/card0/power/rc6_residency_ms
> 
> displays #ms GPU has been in deep rc6 since boot:
> cat /sys/class/drm/card0/power/rc6p_residency_ms
> 
> displays #ms GPU has been in deepest rc6 since boot:
> cat /sys/class/drm/card0/power/rc6pp_residency_ms
> 
> 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 can only guess at the
> reason reason for this. Those writing tools that utilize this value need
> to be careful and probably want to scrutinize the value very carefully.
> 
> v2: use common rc6 residency units to milliseconds for the other RC6 types
> 
> v3: don't create sysfs files for GEN <= 5
> add a rc6_enable to show a mask of enabled rc6 types
> use unmerge instead of remove for sysfs group
> squash intel_enable_rc6() extraction into this patch
> 
> v4: rename sysfs files (Chris)
> 
> CC: Chris Wilson <chris at chris-wilson.co.uk>
> CC: Daniel Vetter <daniel.vetter at ffwll.ch>f
> CC: Arjan van de Ven <arjan at linux.intel.com>
> Signed-off-by: Ben Widawsky <benjamin.widawsky at intel.com>

So the only downside to using the pre-existing power group is that we do
not get the interface if power-management is compiled out of the kernel,
which I suppose is appropriate.

I'm down to just bikeshedding over useless lines of code which do not
even add visual clarity...

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre