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Commit 69e4f900 authored by Ville Syrjälä's avatar Ville Syrjälä Committed by Daniel Vetter
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drm/i915: Make vlv_find_best_dpll() ppm calculation safe 



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

Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent 953d22e8

drivers/gpu/drm/i915/intel_display.c

+8 −8
Original line number Diff line number Diff line
@@ -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) {