From 2a56a0b913a8d7314c2c10fdd57d667b599232b4 Mon Sep 17 00:00:00 2001 From: Ben Skeggs Date: Fri, 1 Oct 2010 14:39:37 +1000 Subject: [PATCH] drm/nva3: fix overflow in fixed point math used for pll calculation And a slight tweak which gets us closer to VBIOS-calculated numbers. Signed-off-by: Ben Skeggs --- drivers/gpu/drm/nouveau/nv50_calc.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nv50_calc.c b/drivers/gpu/drm/nouveau/nv50_calc.c index 2cdc2bfe7179..de81151648f8 100644 --- a/drivers/gpu/drm/nouveau/nv50_calc.c +++ b/drivers/gpu/drm/nouveau/nv50_calc.c @@ -51,24 +51,28 @@ nv50_calc_pll2(struct drm_device *dev, struct pll_lims *pll, int clk, int *N, int *fN, int *M, int *P) { fixed20_12 fb_div, a, b; + u32 refclk = pll->refclk / 10; + u32 max_vco_freq = pll->vco1.maxfreq / 10; + u32 max_vco_inputfreq = pll->vco1.max_inputfreq / 10; + clk /= 10; - *P = pll->vco1.maxfreq / clk; + *P = max_vco_freq / clk; if (*P > pll->max_p) *P = pll->max_p; if (*P < pll->min_p) *P = pll->min_p; - /* *M = ceil(refclk / pll->vco.max_inputfreq); */ - a.full = dfixed_const(pll->refclk); - b.full = dfixed_const(pll->vco1.max_inputfreq); + /* *M = floor((refclk + max_vco_inputfreq) / max_vco_inputfreq); */ + a.full = dfixed_const(refclk + max_vco_inputfreq); + b.full = dfixed_const(max_vco_inputfreq); a.full = dfixed_div(a, b); - a.full = dfixed_ceil(a); + a.full = dfixed_floor(a); *M = dfixed_trunc(a); /* fb_div = (vco * *M) / refclk; */ fb_div.full = dfixed_const(clk * *P); fb_div.full = dfixed_mul(fb_div, a); - a.full = dfixed_const(pll->refclk); + a.full = dfixed_const(refclk); fb_div.full = dfixed_div(fb_div, a); /* *N = floor(fb_div); */