Commit 31d10b57 authored Jan 06, 2016 by Maarten Lankhorst

drm/i915: Allow fuzzy matching in intel_compare_link_m_n



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@linux.intel.com>
Tested-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/568D0E93.304@linux.intel.com

parent d93c0372

drivers/gpu/drm/i915/intel_display.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -12577,19 +12577,22 @@ 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