[Intel-gfx] [PATCH] drm/i915: Pretend cursor is always on for ILK-style WM calculations

[Matt Roper]

Due to our lack of two-step watermark programming, our driver has
historically pretended that the cursor plane is always on for the
purpose of watermark calculations; this helps avoid serious flickering
when the cursor turns off/on (e.g., when the user moves the mouse
pointer to a different screen).  That workaround was accidentally
dropped as we started working toward atomic watermark updates.  Since we
still aren't quite there yet with two-stage updates, we need to
resurrect the workaround and treat the cursor as always active.

Cc: simdev11 at outlook.com
Cc: manfred.kitzbichler at gmail.com
Reported-by: simdev11 at outlook.com
Reported-by: manfred.kitzbichler at gmail.com
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93892
Fixes: 43d59eda1 ("drm/i915: Eliminate usage of plane_wm_parameters from ILK-style WM code (v2)")
Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
I'm traveling at the moment and don't have any HW access, so this patch is
completely untested, but I think it will solve the issue being reported.

 drivers/gpu/drm/i915/intel_pm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 31bc4ea..a53c018 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -1799,16 +1799,21 @@ static uint32_t ilk_compute_cur_wm(const struct intel_crtc_state *cstate,
 				   const struct intel_plane_state *pstate,
 				   uint32_t mem_value)
 {
-	int cpp = pstate->base.fb ?
-		drm_format_plane_cpp(pstate->base.fb->pixel_format, 0) : 0;
+	/*
+	 * We treat the cursor plane as always-on for the purposes of watermark
+	 * calculation.  Until we have two-stage watermark programming merged,
+	 * this is necessary to avoid flickering.
+	 */
+	int cpp = 4;
+	int width = drm_rect_width(&pstate->dst) ?: 64;
 
-	if (!cstate->base.active || !pstate->visible)
+	if (!cstate->base.active)
 		return 0;
 
+
 	return ilk_wm_method2(ilk_pipe_pixel_rate(cstate),
 			      cstate->base.adjusted_mode.crtc_htotal,
-			      drm_rect_width(&pstate->dst),
-			      cpp, mem_value);
+			      width, cpp, mem_value);
 }
 
 /* Only for WM_LP. */
-- 
2.1.4