From: Ville Syrjälä <[email protected]> vlv_find_best_dpll() has several integer over/underflow issues, includes a hand rolled DIV_ROUND_CLOSEST(), has a boat load of variables, some slightly weird math, and it doesn't look very nice either.
Rather than try to deal with each issue separately I just decided to rewrite the function a bit. WARNING: Entirely untested Signed-off-by: Ville Syrjälä <[email protected]> --- drivers/gpu/drm/i915/intel_display.c | 94 +++++++++++++++--------------------- 1 file changed, 40 insertions(+), 54 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index 3b06250..f89fb12 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -670,65 +670,51 @@ vlv_find_best_dpll(const intel_limit_t *limit, struct drm_crtc *crtc, int target, int refclk, intel_clock_t *match_clock, intel_clock_t *best_clock) { - u32 p1, p2, m1, m2, vco, bestn, bestm1, bestm2, bestp1, bestp2; - u32 m, n, fastclk; - u32 updrate, minupdate, p; - unsigned long bestppm, ppm, absppm; - int dotclk, flag; - - flag = 0; - dotclk = target * 1000; - bestppm = 1000000; - ppm = absppm = 0; - fastclk = dotclk / (2*100); - updrate = 0; - minupdate = 19200; - n = p = p1 = p2 = m = m1 = m2 = vco = bestn = 0; - bestm1 = bestm2 = bestp1 = bestp2 = 0; + intel_clock_t clock = { + .dot = target * 5, /* fast clock */ + }; + unsigned int bestppm = 1000000; + /* min update 19.2 MHz */ + int max_n = min(limit->n.max, refclk / 19200); /* based on hardware requirement, prefer smaller n to precision */ - for (n = limit->n.min; n <= ((refclk) / minupdate); n++) { - updrate = refclk / n; - for (p1 = limit->p1.max; p1 > limit->p1.min; p1--) { - for (p2 = limit->p2.p2_fast+1; p2 > 0; p2--) { - if (p2 > 10) - p2 = p2 - 1; - p = p1 * p2; - /* based on hardware requirement, prefer bigger m1,m2 values */ - for (m1 = limit->m1.min; m1 <= limit->m1.max; m1++) { - m2 = (((2*(fastclk * p * n / m1 )) + - refclk) / (2*refclk)); - m = m1 * m2; - vco = updrate * m; - if (vco >= limit->vco.min && vco < limit->vco.max) { - ppm = 1000000 * ((vco / p) - fastclk) / fastclk; - absppm = (ppm > 0) ? ppm : (-ppm); - if (absppm < 100 && ((p1 * p2) > (bestp1 * bestp2))) { - bestppm = 0; - flag = 1; - } - if (absppm < bestppm - 10) { - bestppm = absppm; - flag = 1; - } - if (flag) { - bestn = n; - bestm1 = m1; - bestm2 = m2; - bestp1 = p1; - bestp2 = p2; - flag = 0; - } - } - } + for (clock.n = limit->n.min; clock.n <= max_n; clock.n++) { + for (clock.p1 = limit->p1.max; clock.p1 > limit->p1.min; clock.p1--) { + for (clock.p2 = limit->p2.p2_fast+1; clock.p2 > 0; clock.p2--) { + if (clock.p2 > 10) + clock.p2--; + clock.p = clock.p1 * clock.p2; + + /* based on hardware requirement, prefer bigger m1,m2 values */ + for (clock.m1 = limit->m1.min; clock.m1 <= limit->m1.max; clock.m1++) { + unsigned int ppm, diff; + + clock.m2 = DIV_ROUND_CLOSEST(clock.dot * clock.p * clock.n, + clock.m1 * refclk); + clock.m = clock.m1 * clock.m2; + + clock.vco = refclk * clock.m / clock.n; + + if (clock.vco < limit->vco.min || + clock.vco >= limit->vco.max) + continue; + + diff = abs(clock.vco / clock.p - clock.dot); + ppm = div_u64(1000000ULL * diff, clock.dot); + + if (ppm < 100 && clock.p > best_clock->p) { + bestppm = 0; + *best_clock = clock; + } + + if (ppm + 10 < bestppm) { + bestppm = ppm; + *best_clock = clock; } } } - best_clock->n = bestn; - best_clock->m1 = bestm1; - best_clock->m2 = bestm2; - best_clock->p1 = bestp1; - best_clock->p2 = bestp2; + } + } return true; } -- 1.8.1.5 _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
