drm/i915: Include register polling in reg_rw traces

We generally omit register polling from the i915_reg_rw tracepoint.
Understandable since polling could generate a lot of noise in the
trace. The downside is that the trace is incomplete. As a compromise
let's trace the final register value observed while polling. That
should be generally sufficient to observe what the code should be
doing next.

I suppose in some cases it might make sense to also trace the initial
register value, and maybe the number of times we polled. But that
would require a separate tracepoint so let's leave it for the future.

The other users of _NOTRACE() are i915_pmu and i2c bitbanging,
which I decided to leave alone.

Next we should do something to claw back the tracepoints for
planes and whatnot which were switched to _FW() a while back.
I guess just new macros for raw_rw+trace. The question is
what to call it?

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190204211644.21967-1-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_dp.c

@@ -1061,6 +1061,10 @@ intel_dp_aux_wait_done(struct intel_dp *intel_dp)
 #define C (((status = I915_READ_NOTRACE(ch_ctl)) & DP_AUX_CH_CTL_SEND_BUSY) == 0)
 	done = wait_event_timeout(dev_priv->gmbus_wait_queue, C,
 				  msecs_to_jiffies_timeout(10));
+
+	/* just trace the final value */
+	trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
+
 	if (!done)
 		DRM_ERROR("dp aux hw did not signal timeout!\n");
 #undef C
@@ -1227,6 +1231,8 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 			break;
 		msleep(1);
 	}
+	/* just trace the final value */
+	trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
 
 	if (try == 3) {
 		static u32 last_status = -1;