patches.baytrail/1018-drm-i915-Make-sure-we-respect-n.max-on-VLV.patch

From 395bcfd8e7a5d775dc5e54303a91c2f32b4fb6ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@linux.intel.com>
Date: Tue, 24 Sep 2013 21:26:24 +0300
Subject: drm/i915: Make sure we respect n.max on VLV
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We limit the maximum n divider value in order to make sure the PLL's
reference inout is at least 19.2 MHz. I assume that is done to satisfy
some hardware requirement.

However we never check whether that calculated limit is below the
maximum supoorted N divider value (7). In practice that is always true
since we only support 100 MHz reference clock, but making the code
safe against higher reference clocks seems like a reasoanble thing to
do.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit 27e639bf024a0706015dbb348eb32619a9bb9329)
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e83406697d67..740a9bc2dd0a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -678,15 +678,16 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct drm_crtc *crtc,
 		   intel_clock_t *best_clock)
 {
 	intel_clock_t clock;
-	u32 minupdate = 19200;
 	unsigned int bestppm = 1000000;
+	/* min update 19.2 MHz */
+	int max_n = min(limit->n.max, refclk / 19200);
 
 	target *= 5; /* fast clock */
 
 	memset(best_clock, 0, sizeof(*best_clock));
 
 	/* based on hardware requirement, prefer smaller n to precision */
-	for (clock.n = limit->n.min; clock.n <= ((refclk) / minupdate); clock.n++) {
+	for (clock.n = limit->n.min; clock.n <= max_n; clock.n++) {
 		for (clock.p1 = limit->p1.max; clock.p1 > limit->p1.min; clock.p1--) {
 			for (clock.p2 = limit->p2.p2_fast; clock.p2 > 0;
 			     clock.p2 -= clock.p2 > 10 ? 2 : 1) {
-- 
1.8.5.rc3