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drm/i915: Allow fuzzy matching in intel_compare_link_m_n

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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
This commit is contained in:
Maarten Lankhorst 2016-01-06 13:54:43 +01:00
parent d93c037246
commit 31d10b5701
1 changed files with 8 additions and 5 deletions
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13
drivers/gpu/drm/i915/intel_display.c
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@ -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