linux/drivers/gpu/drm/nouveau/nv50_calc.c
Ben Skeggs 2a56a0b913 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>
2010-11-18 14:38:34 +10:00

92 lines
2.7 KiB
C

/*
* Copyright 2010 Red Hat Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* Authors: Ben Skeggs
*/
#include "drmP.h"
#include "drm_fixed.h"
#include "nouveau_drv.h"
#include "nouveau_hw.h"
int
nv50_calc_pll(struct drm_device *dev, struct pll_lims *pll, int clk,
int *N1, int *M1, int *N2, int *M2, int *P)
{
struct nouveau_pll_vals pll_vals;
int ret;
ret = nouveau_calc_pll_mnp(dev, pll, clk, &pll_vals);
if (ret <= 0)
return ret;
*N1 = pll_vals.N1;
*M1 = pll_vals.M1;
*N2 = pll_vals.N2;
*M2 = pll_vals.M2;
*P = pll_vals.log2P;
return ret;
}
int
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 = max_vco_freq / clk;
if (*P > pll->max_p)
*P = pll->max_p;
if (*P < pll->min_p)
*P = pll->min_p;
/* *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_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(refclk);
fb_div.full = dfixed_div(fb_div, a);
/* *N = floor(fb_div); */
a.full = dfixed_floor(fb_div);
*N = dfixed_trunc(fb_div);
/* *fN = (fmod(fb_div, 1.0) * 8192) - 4096; */
b.full = dfixed_const(8192);
a.full = dfixed_mul(a, b);
fb_div.full = dfixed_mul(fb_div, b);
fb_div.full = fb_div.full - a.full;
*fN = dfixed_trunc(fb_div) - 4096;
*fN &= 0xffff;
return clk;
}