[Intel-gfx] [PATCH] drm/i915: Allow fuzzy matching in intel_compare_link_m_n

[Maarten Lankhorst]

This prevents a unnecessary modeset on a dell XPS 13 (2016).

N is always a power of 2, which means that for fuzzy matching we should
compare for inequality on the n values, then do fuzzy matching on the m
values.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Tested-by: 
--
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7afbdc45a278..aa4f1e69b92e 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12638,19 +12638,22 @@ intel_compare_m_n(unsigned int m, unsigned int n,
 
 	BUILD_BUG_ON(DATA_LINK_M_N_MASK > INT_MAX);
 
-	if (m > m2) {
-		while (m > m2) {
+	if (n > n2) {
+		while (n > n2) {
 			m2 <<= 1;
 			n2 <<= 1;
 		}
-	} else if (m < m2) {
-		while (m < m2) {
+	} else if (n < n2) {
+		while (n < n2) {
 			m <<= 1;
 			n <<= 1;
 		}
 	}
 
-	return m == m2 && n == n2;
+	if (n != n2)
+		return false;
+
+	return intel_fuzzy_clock_check(m, m2);
 }
 
 static bool