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 <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nv50_calc.c b/drivers/gpu/drm/nouveau/nv50_calc.c
index 2cdc2bf..de81151 100644
--- a/drivers/gpu/drm/nouveau/nv50_calc.c
+++ b/drivers/gpu/drm/nouveau/nv50_calc.c
@@ -51,24 +51,28 @@
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); */