linux-kernel - [PATCH] clk: xilinx: Optimize divisor search in clk_wzrd_get_divisors

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Message-ID: <20250729050842.1522-1-shubhrajyoti.datta@amd.com>
Date: Tue, 29 Jul 2025 10:38:42 +0530
From: Shubhrajyoti Datta <shubhrajyoti.datta@....com>
To: <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <git@....com>, Michael Turquette <mturquette@...libre.com>, Stephen Boyd
	<sboyd@...nel.org>, Michal Simek <michal.simek@....com>, Shubhrajyoti Datta
	<shubhrajyoti.datta@....com>
Subject: [PATCH] clk: xilinx: Optimize divisor search in clk_wzrd_get_divisors_ver()

Optimise the clock wizard divisor calculation by eliminating the innermost
loop over output divider o. Earlier there was an error that is returned
if the WZRD_MIN_ERR is not achieved error is returned now it computes
the best possible frequency.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@....com>
---
For someof the input frequency choices
setting 233250000 -> 233331003 diff is 81003
if minerr is 20000 it was returning error now it will 
compute the nearest frequency. 


 drivers/clk/xilinx/clk-xlnx-clock-wizard.c | 32 ++++++++++++----------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/drivers/clk/xilinx/clk-xlnx-clock-wizard.c b/drivers/clk/xilinx/clk-xlnx-clock-wizard.c
index 3efce7b88906..4775cde45e21 100644
--- a/drivers/clk/xilinx/clk-xlnx-clock-wizard.c
+++ b/drivers/clk/xilinx/clk-xlnx-clock-wizard.c
@@ -344,7 +344,7 @@ static int clk_wzrd_get_divisors_ver(struct clk_hw *hw, unsigned long rate,
 				     unsigned long parent_rate)
 {
 	struct clk_wzrd_divider *divider = to_clk_wzrd_divider(hw);
-	u64 vco_freq, freq, diff, vcomin, vcomax;
+	u64 vco_freq, freq, diff, vcomin, vcomax, best_diff = -1ULL;
 	u32 m, d, o;
 	u32 mmin, mmax, dmin, dmax, omin, omax;
 
@@ -360,22 +360,26 @@ static int clk_wzrd_get_divisors_ver(struct clk_hw *hw, unsigned long rate,
 	for (m = mmin; m <= mmax; m++) {
 		for (d = dmin; d <= dmax; d++) {
 			vco_freq = DIV_ROUND_CLOSEST((parent_rate * m), d);
-			if (vco_freq >= vcomin && vco_freq <= vcomax) {
-				for (o = omin; o <= omax; o++) {
-					freq = DIV_ROUND_CLOSEST_ULL(vco_freq, o);
-					diff = abs(freq - rate);
-
-					if (diff < WZRD_MIN_ERR) {
-						divider->m = m;
-						divider->d = d;
-						divider->o = o;
-						return 0;
-					}
-				}
+			if (vco_freq < vcomin || vco_freq > vcomax)
+				continue;
+
+			o = DIV_ROUND_CLOSEST_ULL(vco_freq, rate);
+			if (o < omin || o > omax)
+				continue;
+			freq = DIV_ROUND_CLOSEST_ULL(vco_freq, o);
+			diff = abs(freq - rate);
+
+			if (diff < best_diff) {
+				best_diff = diff;
+				divider->m = m;
+				divider->d = d;
+				divider->o = o;
+				if (!diff)
+					return 0;
 			}
 		}
 	}
-	return -EBUSY;
+	return 0;
 }
 
 static int clk_wzrd_get_divisors(struct clk_hw *hw, unsigned long rate,
-- 
2.34.1