From 1a1f12872edcd5e425b668a35fb23548cfa918ef Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 7 Nov 2017 14:03:38 +0000
Subject: [PATCH] drm/i915: Prevent unbounded wm results in g4x_compute_wm()
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Git-commit: 1a1f12872edcd5e425b668a35fb23548cfa918ef
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900

Smatch warns of

drivers/gpu/drm/i915/intel_pm.c:1161 g4x_compute_wm() warn: signedness bug returning '(-33554430)'

which is a result of it believing that wm may be INT_MAX following
g4x_tlb_miss_wa(). Just declaring g4x_tlb_miss_wa() as returning an
unsigned integer is not sufficient, we need to tell smatch that wm itself
is unsigned for it to not worry. So mark up the locals we expect to be
non-negative, and so silence smatch.

V2: Mark up vlv_compute_wm_level() as unsigned similarly.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrj채l채 <ville.syrjala@linux.intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Ville Syrj채l채 <ville.syrjala@linux.intel.com> #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20171107140338.13748-1-chris@chris-wilson.co.uk
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/intel_pm.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -922,7 +922,7 @@ static void pineview_update_wm(struct in
  *  and the size of 8 whole lines. This adjustment is always performed
  *  in the actual pixel depth regardless of whether FBC is enabled or not."
  */
-static int g4x_tlb_miss_wa(int fifo_size, int width, int cpp)
+static unsigned int g4x_tlb_miss_wa(int fifo_size, int width, int cpp)
 {
 	int tlb_miss = fifo_size * 64 - width * cpp * 8;
 
@@ -1099,8 +1099,8 @@ static uint16_t g4x_compute_wm(const str
 	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
 	const struct drm_display_mode *adjusted_mode =
 		&crtc_state->base.adjusted_mode;
-	int clock, htotal, cpp, width, wm;
-	int latency = dev_priv->wm.pri_latency[level] * 10;
+	unsigned int latency = dev_priv->wm.pri_latency[level] * 10;
+	unsigned int clock, htotal, cpp, width, wm;
 
 	if (latency == 0)
 		return USHRT_MAX;
@@ -1139,7 +1139,7 @@ static uint16_t g4x_compute_wm(const str
 		   level == G4X_WM_LEVEL_NORMAL) {
 		wm = intel_wm_method1(clock, cpp, latency);
 	} else {
-		int small, large;
+		unsigned int small, large;
 
 		small = intel_wm_method1(clock, cpp, latency);
 		large = intel_wm_method2(clock, htotal, width, cpp, latency);
@@ -1152,7 +1152,7 @@ static uint16_t g4x_compute_wm(const str
 
 	wm = DIV_ROUND_UP(wm, 64) + 2;
 
-	return min_t(int, wm, USHRT_MAX);
+	return min_t(unsigned int, wm, USHRT_MAX);
 }
 
 static bool g4x_raw_plane_wm_set(struct intel_crtc_state *crtc_state,
@@ -1596,7 +1596,7 @@ static uint16_t vlv_compute_wm_level(con
 	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
 	const struct drm_display_mode *adjusted_mode =
 		&crtc_state->base.adjusted_mode;
-	int clock, htotal, cpp, width, wm;
+	unsigned int clock, htotal, cpp, width, wm;
 
 	if (dev_priv->wm.pri_latency[level] == 0)
 		return USHRT_MAX;
@@ -1622,7 +1622,7 @@ static uint16_t vlv_compute_wm_level(con
 				    dev_priv->wm.pri_latency[level] * 10);
 	}
 
-	return min_t(int, wm, USHRT_MAX);
+	return min_t(unsigned int, wm, USHRT_MAX);
 }
 
 static bool vlv_need_sprite0_fifo_workaround(unsigned int active_planes)