Commit 32167016 authored by Christian König's avatar Christian König

drm/radeon: rework finding display PLL numbers v2

This completely reworks how the PLL parameters are generated and
should result in better matching dot clock frequencies.

Probably needs quite a bit of testing.

bugs: https://bugs.freedesktop.org/show_bug.cgi?id=76564

v2: more cleanup and comments.
Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
Reviewed-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent ec9954fc
......@@ -34,6 +34,8 @@
#include <drm/drm_crtc_helper.h>
#include <drm/drm_edid.h>
#include <linux/gcd.h>
static void avivo_crtc_load_lut(struct drm_crtc *crtc)
{
struct radeon_crtc *radeon_crtc = to_radeon_crtc(crtc);
......@@ -799,66 +801,57 @@ int radeon_ddc_get_modes(struct radeon_connector *radeon_connector)
}
/* avivo */
static void avivo_get_fb_div(struct radeon_pll *pll,
u32 target_clock,
u32 post_div,
u32 ref_div,
u32 *fb_div,
u32 *frac_fb_div)
{
u32 tmp = post_div * ref_div;
tmp *= target_clock;
*fb_div = tmp / pll->reference_freq;
*frac_fb_div = tmp % pll->reference_freq;
if (*fb_div > pll->max_feedback_div)
*fb_div = pll->max_feedback_div;
else if (*fb_div < pll->min_feedback_div)
*fb_div = pll->min_feedback_div;
}
static u32 avivo_get_post_div(struct radeon_pll *pll,
u32 target_clock)
/**
* avivo_reduce_ratio - fractional number reduction
*
* @nom: nominator
* @den: denominator
* @nom_min: minimum value for nominator
* @den_min: minimum value for denominator
*
* Find the greatest common divisor and apply it on both nominator and
* denominator, but make nominator and denominator are at least as large
* as their minimum values.
*/
static void avivo_reduce_ratio(unsigned *nom, unsigned *den,
unsigned nom_min, unsigned den_min)
{
u32 vco, post_div, tmp;
unsigned tmp;
if (pll->flags & RADEON_PLL_USE_POST_DIV)
return pll->post_div;
/* reduce the numbers to a simpler ratio */
tmp = gcd(*nom, *den);
*nom /= tmp;
*den /= tmp;
if (pll->flags & RADEON_PLL_PREFER_MINM_OVER_MAXP) {
if (pll->flags & RADEON_PLL_IS_LCD)
vco = pll->lcd_pll_out_min;
else
vco = pll->pll_out_min;
} else {
if (pll->flags & RADEON_PLL_IS_LCD)
vco = pll->lcd_pll_out_max;
else
vco = pll->pll_out_max;
/* make sure nominator is large enough */
if (*nom < nom_min) {
tmp = (nom_min + *nom - 1) / *nom;
*nom *= tmp;
*den *= tmp;
}
post_div = vco / target_clock;
tmp = vco % target_clock;
if (pll->flags & RADEON_PLL_PREFER_MINM_OVER_MAXP) {
if (tmp)
post_div++;
} else {
if (!tmp)
post_div--;
/* make sure the denominator is large enough */
if (*den < den_min) {
tmp = (den_min + *den - 1) / *den;
*nom *= tmp;
*den *= tmp;
}
if (post_div > pll->max_post_div)
post_div = pll->max_post_div;
else if (post_div < pll->min_post_div)
post_div = pll->min_post_div;
return post_div;
}
#define MAX_TOLERANCE 10
/**
* radeon_compute_pll_avivo - compute PLL paramaters
*
* @pll: information about the PLL
* @dot_clock_p: resulting pixel clock
* fb_div_p: resulting feedback divider
* frac_fb_div_p: fractional part of the feedback divider
* ref_div_p: resulting reference divider
* post_div_p: resulting reference divider
*
* Try to calculate the PLL parameters to generate the given frequency:
* dot_clock = (ref_freq * feedback_div) / (ref_div * post_div)
*/
void radeon_compute_pll_avivo(struct radeon_pll *pll,
u32 freq,
u32 *dot_clock_p,
......@@ -867,53 +860,123 @@ void radeon_compute_pll_avivo(struct radeon_pll *pll,
u32 *ref_div_p,
u32 *post_div_p)
{
u32 target_clock = freq / 10;
u32 post_div = avivo_get_post_div(pll, target_clock);
u32 ref_div = pll->min_ref_div;
u32 fb_div = 0, frac_fb_div = 0, tmp;
unsigned fb_div_min, fb_div_max, fb_div;
unsigned post_div_min, post_div_max, post_div;
unsigned ref_div_min, ref_div_max, ref_div;
unsigned post_div_best, diff_best;
unsigned nom, den, tmp;
if (pll->flags & RADEON_PLL_USE_REF_DIV)
ref_div = pll->reference_div;
/* determine allowed feedback divider range */
fb_div_min = pll->min_feedback_div;
fb_div_max = pll->max_feedback_div;
if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV) {
avivo_get_fb_div(pll, target_clock, post_div, ref_div, &fb_div, &frac_fb_div);
frac_fb_div = (100 * frac_fb_div) / pll->reference_freq;
if (frac_fb_div >= 5) {
frac_fb_div -= 5;
frac_fb_div = frac_fb_div / 10;
frac_fb_div++;
}
if (frac_fb_div >= 10) {
fb_div++;
frac_fb_div = 0;
fb_div_min *= 10;
fb_div_max *= 10;
}
/* determine allowed ref divider range */
if (pll->flags & RADEON_PLL_USE_REF_DIV)
ref_div_min = pll->reference_div;
else
ref_div_min = pll->min_ref_div;
ref_div_max = pll->max_ref_div;
/* determine allowed post divider range */
if (pll->flags & RADEON_PLL_USE_POST_DIV) {
post_div_min = pll->post_div;
post_div_max = pll->post_div;
} else {
while (ref_div <= pll->max_ref_div) {
avivo_get_fb_div(pll, target_clock, post_div, ref_div,
&fb_div, &frac_fb_div);
if (frac_fb_div >= (pll->reference_freq / 2))
fb_div++;
frac_fb_div = 0;
tmp = (pll->reference_freq * fb_div) / (post_div * ref_div);
tmp = (tmp * 10000) / target_clock;
if (tmp > (10000 + MAX_TOLERANCE))
ref_div++;
else if (tmp >= (10000 - MAX_TOLERANCE))
break;
unsigned target_clock = freq / 10;
unsigned vco_min, vco_max;
if (pll->flags & RADEON_PLL_IS_LCD) {
vco_min = pll->lcd_pll_out_min;
vco_max = pll->lcd_pll_out_max;
} else {
vco_min = pll->pll_out_min;
vco_max = pll->pll_out_max;
}
post_div_min = vco_min / target_clock;
if ((target_clock * post_div_min) < vco_min)
++post_div_min;
if (post_div_min < pll->min_post_div)
post_div_min = pll->min_post_div;
post_div_max = vco_max / target_clock;
if ((target_clock * post_div_max) > vco_max)
--post_div_max;
if (post_div_max > pll->max_post_div)
post_div_max = pll->max_post_div;
}
/* represent the searched ratio as fractional number */
nom = pll->flags & RADEON_PLL_USE_FRAC_FB_DIV ? freq : freq / 10;
den = pll->reference_freq;
/* reduce the numbers to a simpler ratio */
avivo_reduce_ratio(&nom, &den, fb_div_min, post_div_min);
/* now search for a post divider */
if (pll->flags & RADEON_PLL_PREFER_MINM_OVER_MAXP)
post_div_best = post_div_min;
else
ref_div++;
post_div_best = post_div_max;
diff_best = ~0;
for (post_div = post_div_min; post_div <= post_div_max; ++post_div) {
unsigned diff = abs(den - den / post_div * post_div);
if (diff < diff_best || (diff == diff_best &&
!(pll->flags & RADEON_PLL_PREFER_MINM_OVER_MAXP))) {
post_div_best = post_div;
diff_best = diff;
}
}
post_div = post_div_best;
*dot_clock_p = ((pll->reference_freq * fb_div * 10) + (pll->reference_freq * frac_fb_div)) /
(ref_div * post_div * 10);
/* get matching reference and feedback divider */
ref_div = max(den / post_div, 1u);
fb_div = nom;
/* we're almost done, but reference and feedback
divider might be to large now */
tmp = ref_div;
if (fb_div > fb_div_max) {
ref_div = ref_div * fb_div_max / fb_div;
fb_div = fb_div_max;
}
if (ref_div > ref_div_max) {
ref_div = ref_div_max;
fb_div = nom * ref_div_max / tmp;
}
/* reduce the numbers to a simpler ratio once more */
/* this also makes sure that the reference divider is large enough */
avivo_reduce_ratio(&fb_div, &ref_div, fb_div_min, ref_div_min);
/* and finally save the result */
if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV) {
*fb_div_p = fb_div / 10;
*frac_fb_div_p = fb_div % 10;
} else {
*fb_div_p = fb_div;
*frac_fb_div_p = frac_fb_div;
*frac_fb_div_p = 0;
}
*dot_clock_p = ((pll->reference_freq * *fb_div_p * 10) +
(pll->reference_freq * *frac_fb_div_p)) /
(ref_div * post_div * 10);
*ref_div_p = ref_div;
*post_div_p = post_div;
DRM_DEBUG_KMS("%d, pll dividers - fb: %d.%d ref: %d, post %d\n",
*dot_clock_p, fb_div, frac_fb_div, ref_div, post_div);
DRM_DEBUG_KMS("%d - %d, pll dividers - fb: %d.%d ref: %d, post %d\n",
freq, *dot_clock_p, *fb_div_p, *frac_fb_div_p,
ref_div, post_div);
}
/* pre-avivo */
......
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