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drm/i915: Make vlv_find_best_dpll() ppm calculation safe

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Use div_u64() to make the ppm calculation in vlv_find_best_dpll() safe
against interger overflows.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Ville Syrjälä 2013-09-24 21:26:20 +03:00 committed by Daniel Vetter
parent 953d22e870
commit 69e4f900be
1 changed files with 8 additions and 8 deletions
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16
drivers/gpu/drm/i915/intel_display.c
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@ -672,13 +672,11 @@ 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;
@ -695,6 +693,8 @@ 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;
@ -702,14 +702,14 @@ 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) {