From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Use div_u64() to make the ppm calculation in vlv_find_best_dpll() safe
against interger overflows.
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_display.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 4b1af94..f8d67b2 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -673,13 +673,11 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct drm_crtc *crtc,
u32 p1, p2, m1, m2, vco, bestn, bestm1, bestm2, bestp1, bestp2;
u32 m, n, fastclk;
u32 updrate, minupdate, p;
- unsigned long bestppm, ppm, absppm;
+ unsigned int bestppm = 1000000;
int dotclk, flag;
flag = 0;
dotclk = target * 1000;
- bestppm = 1000000;
- ppm = absppm = 0;
fastclk = dotclk / (2*100);
updrate = 0;
minupdate = 19200;
@@ -696,6 +694,8 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct drm_crtc *crtc,
p = p1 * p2;
/* based on hardware requirement, prefer bigger m1,m2 values */
for (m1 = limit->m1.min; m1 <= limit->m1.max; m1++) {
+ unsigned int ppm, diff;
+
m2 = DIV_ROUND_CLOSEST(fastclk * p * n, refclk * m1);
m = m1 * m2;
vco = updrate * m;
@@ -703,14 +703,14 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct drm_crtc *crtc,
if (vco < limit->vco.min || vco >= limit->vco.max)
continue;
- ppm = 1000000 * ((vco / p) - fastclk) / fastclk;
- absppm = (ppm > 0) ? ppm : (-ppm);
- if (absppm < 100 && ((p1 * p2) > (bestp1 * bestp2))) {
+ diff = abs(vco / p - fastclk);
+ ppm = div_u64(1000000ULL * diff, fastclk);
+ if (ppm < 100 && ((p1 * p2) > (bestp1 * bestp2))) {
bestppm = 0;
flag = 1;
}
- if (absppm < bestppm - 10) {
- bestppm = absppm;
+ if (ppm < bestppm - 10) {
+ bestppm = ppm;
flag = 1;
}
if (flag) {
--
1.8.1.5
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