From 69e4f900be175fd80fe69221a329c8993b16925b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Tue, 24 Sep 2013 21:26:20 +0300 Subject: [PATCH] drm/i915: Make vlv_find_best_dpll() ppm calculation safe MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Use div_u64() to make the ppm calculation in vlv_find_best_dpll() safe against interger overflows. Signed-off-by: Ville Syrjälä Reviewed-by: Mika Kuoppala Signed-off-by: Daniel Vetter --- 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 617b963dfb67..dc5077560c74 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -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) { -- GitLab