linux-kernel - [PATCH 1/2] drm/i915: Fix bug while calculating the clock value using do_div in ironlake_crtc_clock

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Message-Id: <1376962382-29913-1-git-send-email-furquan@google.com>
Date:	Mon, 19 Aug 2013 18:33:01 -0700
From:	Furquan Shaikh <furquan@...gle.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Paulo Zanoni <paulo.r.zanoni@...el.com>,
	Josh Triplett <josh.triplett@...el.com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	intel-gfx@...ts.freedesktop.org
Cc:	Ronald Minnich <rminnich@...gle.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Furquan Shaikh <furquan@...gle.com>, furquan.m.shaikh@...il.com
Subject: [PATCH 1/2] drm/i915: Fix bug while calculating the clock value using do_div in ironlake_crtc_clock_get

We need to round up the values since the comparison in drm_mode_equal might fail if division
results in fractional part

Signed-off-by: Furquan Shaikh <furquan@...gle.com>
---
 drivers/gpu/drm/i915/intel_display.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 0f40f8e..e0069f4 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7190,7 +7190,11 @@ static void ironlake_crtc_clock_get(struct intel_crtc *crtc,
 		return;
 
 	clock = ((u64)link_m * (u64)link_freq * (u64)repeat);
-	do_div(clock, link_n);
+	/* This is required because the value comes out to be in fraction
+	   (eg. 70699.54). Need to round it up since values are compared in
+	   drm_mode_equal
+	*/
+	clock = DIV_ROUND_UP_ULL(clock, link_n);
 
 	pipe_config->adjusted_mode.clock = clock;
 }
-- 
1.8.3

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