[PATCH] drm/radeon: rework finding display PLL numbers v2
Christian König
deathsimple at vodafone.de
Sun Mar 30 01:22:09 PDT 2014
From: Christian König <christian.koenig at amd.com>
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: Christian König <christian.koenig at amd.com>
---
drivers/gpu/drm/radeon/radeon_display.c | 243 ++++++++++++++++++++------------
1 file changed, 153 insertions(+), 90 deletions(-)
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index fbd8b93..4e83ffd 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -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;
-
- if (pll->flags & RADEON_PLL_USE_POST_DIV)
- return pll->post_div;
-
- 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;
+ unsigned tmp;
+
+ /* reduce the numbers to a simpler ratio */
+ tmp = gcd(*nom, *den);
+ *nom /= tmp;
+ *den /= tmp;
+
+ /* 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++;
+ 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 {
+ 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;
}
- if (frac_fb_div >= 10) {
- fb_div++;
- frac_fb_div = 0;
+
+ 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
+ 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;
+
+ /* 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 {
- 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;
- else
- ref_div++;
- }
+ *fb_div_p = fb_div;
+ *frac_fb_div_p = 0;
}
- *dot_clock_p = ((pll->reference_freq * fb_div * 10) + (pll->reference_freq * frac_fb_div)) /
- (ref_div * post_div * 10);
- *fb_div_p = fb_div;
- *frac_fb_div_p = frac_fb_div;
+ *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 */
--
1.9.1
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