patches.baytrail/0587-drm-i915-Disable-specific-watermark-levels-when-late.patch

From 31c3a7f61f43a4cf229e4f6168c8cc70c6ecfef9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Thu, 1 Aug 2013 16:18:53 +0300
Subject: drm/i915: Disable specific watermark levels when latency is zero
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Return UINT_MAX for the calculated WM level if the latency is zero.
This will lead to marking the WM level as disabled.

I'm not sure if latency==0 should mean that we want to disable the
level. But that's the implication I got from the fact that we don't
even enable the watermark code of the SSKDP register is 0.

v2: Use WARN() to scare people

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit 3312ba65caa23cf1210cc578755babc394769843)
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 76bd4de232e1..42f541671236 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2131,6 +2131,9 @@ static uint32_t ilk_wm_method1(uint32_t pixel_rate, uint8_t bytes_per_pixel,
 {
 	uint64_t ret;
 
+	if (WARN(latency == 0, "Latency value missing\n"))
+		return UINT_MAX;
+
 	ret = (uint64_t) pixel_rate * bytes_per_pixel * latency;
 	ret = DIV_ROUND_UP_ULL(ret, 64 * 10000) + 2;
 
@@ -2143,6 +2146,9 @@ static uint32_t ilk_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal,
 {
 	uint32_t ret;
 
+	if (WARN(latency == 0, "Latency value missing\n"))
+		return UINT_MAX;
+
 	ret = (latency * pixel_rate) / (pipe_htotal * 10000);
 	ret = (ret + 1) * horiz_pixels * bytes_per_pixel;
 	ret = DIV_ROUND_UP(ret, 64) + 2;
-- 
1.8.5.rc3