From: Damien Lespiau <damien.lespiau@intel.com>
Date: Thu, 25 Jun 2015 15:19:24 +0000 (+0100)
Subject: drm/i915/skl: Prefer even dividers for SKL DPLLs
X-Git-Tag: v4.3-rc1~75^2~36^2~142
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=267db663458a8077a087674fb85ea95f540d8671;p=karo-tx-linux.git

drm/i915/skl: Prefer even dividers for SKL DPLLs

Currently, if an odd divider improves the deviation (minimizes it), we
take that divider. The recommendation is to prefer even dividers.

v2: Move the check at the right place after having inverted the two for
    loops in the previous patch.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 6e964ef7dfda..f6b3ccc4ab66 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1317,6 +1317,13 @@ skl_ddi_calculate_wrpll(int clock /* in Hz */,
 						      p);
 			}
 		}
+
+		/*
+		 * If a solution is found with an even divider, prefer
+		 * this one.
+		 */
+		if (d == 0 && ctx.p)
+			break;
 	}
 
 	if (!ctx.p) {