drm/radeon: improve PLL limit handling in post div calculation
This improves the PLL parameters when we work at
the limits of the allowed ranges.
Signed-off-by: Christian König <christian.koenig@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index e6c3c54..8d99d5e 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -840,6 +840,38 @@
}
/**
+ * avivo_get_fb_ref_div - feedback and ref divider calculation
+ *
+ * @nom: nominator
+ * @den: denominator
+ * @post_div: post divider
+ * @fb_div_max: feedback divider maximum
+ * @ref_div_max: reference divider maximum
+ * @fb_div: resulting feedback divider
+ * @ref_div: resulting reference divider
+ *
+ * Calculate feedback and reference divider for a given post divider. Makes
+ * sure we stay within the limits.
+ */
+static void avivo_get_fb_ref_div(unsigned nom, unsigned den, unsigned post_div,
+ unsigned fb_div_max, unsigned ref_div_max,
+ unsigned *fb_div, unsigned *ref_div)
+{
+ /* limit reference * post divider to a maximum */
+ ref_div_max = min(210 / post_div, ref_div_max);
+
+ /* get matching reference and feedback divider */
+ *ref_div = min(max(DIV_ROUND_CLOSEST(den, post_div), 1u), ref_div_max);
+ *fb_div = DIV_ROUND_CLOSEST(nom * *ref_div * post_div, den);
+
+ /* limit fb divider to its maximum */
+ if (*fb_div > fb_div_max) {
+ *ref_div = DIV_ROUND_CLOSEST(*ref_div * fb_div_max, *fb_div);
+ *fb_div = fb_div_max;
+ }
+}
+
+/**
* radeon_compute_pll_avivo - compute PLL paramaters
*
* @pll: information about the PLL
@@ -860,6 +892,9 @@
u32 *ref_div_p,
u32 *post_div_p)
{
+ unsigned target_clock = pll->flags & RADEON_PLL_USE_FRAC_FB_DIV ?
+ freq : freq / 10;
+
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;
@@ -892,7 +927,6 @@
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) {
@@ -903,6 +937,11 @@
vco_max = pll->pll_out_max;
}
+ if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV) {
+ vco_min *= 10;
+ vco_max *= 10;
+ }
+
post_div_min = vco_min / target_clock;
if ((target_clock * post_div_min) < vco_min)
++post_div_min;
@@ -917,7 +956,7 @@
}
/* represent the searched ratio as fractional number */
- nom = pll->flags & RADEON_PLL_USE_FRAC_FB_DIV ? freq : freq / 10;
+ nom = target_clock;
den = pll->reference_freq;
/* reduce the numbers to a simpler ratio */
@@ -931,7 +970,12 @@
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);
+ unsigned diff;
+ avivo_get_fb_ref_div(nom, den, post_div, fb_div_max,
+ ref_div_max, &fb_div, &ref_div);
+ diff = abs(target_clock - (pll->reference_freq * fb_div) /
+ (ref_div * post_div));
+
if (diff < diff_best || (diff == diff_best &&
!(pll->flags & RADEON_PLL_PREFER_MINM_OVER_MAXP))) {
@@ -941,28 +985,9 @@
}
post_div = post_div_best;
- /* limit reference * post divider to a maximum */
- ref_div_max = min(210 / post_div, ref_div_max);
-
- /* get matching reference and feedback divider */
- ref_div = max(DIV_ROUND_CLOSEST(den, post_div), 1u);
- fb_div = DIV_ROUND_CLOSEST(nom * ref_div * post_div, den);
-
- /* we're almost done, but reference and feedback
- divider might be to large now */
-
- nom = fb_div;
- den = ref_div;
-
- if (fb_div > fb_div_max) {
- ref_div = DIV_ROUND_CLOSEST(den * fb_div_max, nom);
- fb_div = fb_div_max;
- }
-
- if (ref_div > ref_div_max) {
- ref_div = ref_div_max;
- fb_div = DIV_ROUND_CLOSEST(nom * ref_div_max, den);
- }
+ /* get the feedback and reference divider for the optimal value */
+ avivo_get_fb_ref_div(nom, den, post_div, fb_div_max, ref_div_max,
+ &fb_div, &ref_div);
/* reduce the numbers to a simpler ratio once more */
/* this also makes sure that the reference divider is large enough */
@@ -984,7 +1009,7 @@
*post_div_p = 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,
+ freq, *dot_clock_p * 10, *fb_div_p, *frac_fb_div_p,
ref_div, post_div);
}