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Subject[PATCH 1/2] clk: si5351: fix .round_rate for multisynth 6-7
Date
The divider calculation for multisynth 6 and 7 differs from the
calculation for multisynth 0-5.

For MS6 and MS7, set MSx_P1 directly, MSx_P1=divide value
[AN619, p. 6].

Referenced document:
[AN619] Manually Generating an Si5351 Register Map, Rev. 0.4

Signed-off-by: Sergej Sawazki <ce3a@gmx.de>
---
drivers/clk/clk-si5351.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/clk-si5351.c b/drivers/clk/clk-si5351.c
index 30335d3..48c5298 100644
--- a/drivers/clk/clk-si5351.c
+++ b/drivers/clk/clk-si5351.c
@@ -552,7 +552,8 @@ static const struct clk_ops si5351_pll_ops = {
* MSx_P2[19:0] = 128 * b - c * floor(128 * b/c) = (128*b) mod c
* MSx_P3[19:0] = c
*
- * MS[6,7] are integer (P1) divide only, P2 = 0, P3 = 0
+ * MS[6,7] are integer (P1) divide only, P1 = divide value,
+ * P2 and P3 are not applicable
*
* for 150MHz < fOUT <= 160MHz:
*
@@ -679,6 +680,16 @@ static long si5351_msynth_round_rate(struct clk_hw *hw, unsigned long rate,
c = 1;

*parent_rate = a * rate;
+ } else if (hwdata->num >= 6) {
+ /* determine the closest integer divider */
+ a = DIV_ROUND_CLOSEST(*parent_rate, rate);
+ if (a < SI5351_MULTISYNTH_A_MIN)
+ a = SI5351_MULTISYNTH_A_MIN;
+ if (a > SI5351_MULTISYNTH67_A_MAX)
+ a = SI5351_MULTISYNTH67_A_MAX;
+
+ b = 0;
+ c = 1;
} else {
unsigned long rfrac, denom;

@@ -692,9 +703,7 @@ static long si5351_msynth_round_rate(struct clk_hw *hw, unsigned long rate,
a = *parent_rate / rate;
if (a < SI5351_MULTISYNTH_A_MIN)
a = SI5351_MULTISYNTH_A_MIN;
- if (hwdata->num >= 6 && a > SI5351_MULTISYNTH67_A_MAX)
- a = SI5351_MULTISYNTH67_A_MAX;
- else if (a > SI5351_MULTISYNTH_A_MAX)
+ if (a > SI5351_MULTISYNTH_A_MAX)
a = SI5351_MULTISYNTH_A_MAX;

/* find best approximation for b/c = fVCO mod fOUT */
@@ -723,6 +732,10 @@ static long si5351_msynth_round_rate(struct clk_hw *hw, unsigned long rate,
hwdata->params.p3 = 1;
hwdata->params.p2 = 0;
hwdata->params.p1 = 0;
+ } else if (hwdata->num >= 6) {
+ hwdata->params.p3 = 0;
+ hwdata->params.p2 = 0;
+ hwdata->params.p1 = a;
} else {
hwdata->params.p3 = c;
hwdata->params.p2 = (128 * b) % c;
--
1.9.1


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