drm/msm: dpu: Simplify frame_done watchdog timeout calculation

Instead of setting the timeout and then immediately reading it back
(along with the hand-rolled msecs_to_jiffies calculation), just
calculate it once and set it in both places at the same time.
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190128204306.95076-2-sean@poorly.runSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c

@@ -1788,6 +1788,7 @@ void dpu_encoder_kickoff(struct drm_encoder *drm_enc, bool async)
 {
 	struct dpu_encoder_virt *dpu_enc;
 	struct dpu_encoder_phys *phys;
+	unsigned long timeout_ms;
 	ktime_t wakeup_time;
 	unsigned int i;
 
@@ -1800,11 +1801,12 @@ void dpu_encoder_kickoff(struct drm_encoder *drm_enc, bool async)
 
 	trace_dpu_enc_kickoff(DRMID(drm_enc));
 
-	atomic_set(&dpu_enc->frame_done_timeout,
-			DPU_FRAME_DONE_TIMEOUT * 1000 /
-			drm_mode_vrefresh(&drm_enc->crtc->state->adjusted_mode));
-	mod_timer(&dpu_enc->frame_done_timer, jiffies +
-		((atomic_read(&dpu_enc->frame_done_timeout) * HZ) / 1000));
+	timeout_ms = DPU_FRAME_DONE_TIMEOUT * 1000 /
+		drm_mode_vrefresh(&drm_enc->crtc->state->adjusted_mode);
+
+	atomic_set(&dpu_enc->frame_done_timeout, timeout_ms);
+	mod_timer(&dpu_enc->frame_done_timer,
+		  jiffies + msecs_to_jiffies(timeout_ms));
 
 	/* All phys encs are ready to go, trigger the kickoff */
 	_dpu_encoder_kickoff_phys(dpu_enc, async);