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drm/nva3: fix overflow in fixed point math used for pll calculation

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And a slight tweak which gets us closer to VBIOS-calculated numbers.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
This commit is contained in:
Ben Skeggs 2010-10-01 14:39:37 +10:00
parent 699ddfd980
commit 2a56a0b913
1 changed files with 10 additions and 6 deletions
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16
drivers/gpu/drm/nouveau/nv50_calc.c
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@ -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); */