drm/i915: Rename and comment all the RPS *stuff*

The names of the struct members for RPS are stupid. Every time I need to
do anything in this code I have to spend a significant amount of time to
remember what it all means. By renaming the variables (and adding the
comments) I hope to clear up the situation. Indeed doing this make some
upcoming patches more readable.

I've avoided ILK because it's possible that the naming used for Ironlake
matches what is in the docs. I believe the ILK power docs were never
published, and I am too lazy to dig them up.

v2: leave rp0, and rp1 in the names. It is useful to have these limits
available at times. min_freq and max_freq (which may be equal to rp0, or
rp1 depending on the platform) represent the actual HW min and max.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 241f5e1..c5c5760 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -980,14 +980,24 @@
 	struct work_struct work;
 	u32 pm_iir;
 
-	u8 cur_delay;
-	u8 min_delay;
-	u8 max_delay;
-	u8 rpe_delay;
-	u8 rp1_delay;
-	u8 rp0_delay;
-	u8 hw_max;
-	u8 min_freq;
+	/* Frequencies are stored in potentially platform dependent multiples.
+	 * In other words, *_freq needs to be multiplied by X to be interesting.
+	 * Soft limits are those which are used for the dynamic reclocking done
+	 * by the driver (raise frequencies under heavy loads, and lower for
+	 * lighter loads). Hard limits are those imposed by the hardware.
+	 *
+	 * A distinction is made for overclocking, which is never enabled by
+	 * default, and is considered to be above the hard limit if it's
+	 * possible at all.
+	 */
+	u8 cur_freq;		/* Current frequency (cached, may not == HW) */
+	u8 min_freq_softlimit;	/* Minimum frequency permitted by the driver */
+	u8 max_freq_softlimit;	/* Max frequency permitted by the driver */
+	u8 max_freq;		/* Maximum frequency, RP0 if not overclocking */
+	u8 min_freq;		/* AKA RPn. Minimum frequency */
+	u8 efficient_freq;	/* AKA RPe. Pre-determined balanced frequency */
+	u8 rp1_freq;		/* "less than" RP0 power/freqency */
+	u8 rp0_freq;		/* Non-overclocked max frequency. */
 
 	bool rp_up_masked;
 	bool rp_down_masked;