[PATCH 4/6] clk: rockchip: pll: let rockchip_rk3588_pll_k_get update m directly

[Alexey Charkov]

Selecting the next integer multiplier m is coupled to setting a negative
fractional coefficient k. The current code checks for negative k in two
separate places, which is error-prone.

Let rockchip_rk3588_pll_k_get update m directly, to make it the single
source of truth for the final value of the integer multiplier m, which
also reduces the number of scattered conditional branches in the code.

Signed-off-by: Alexey Charkov <alchark at flipper.net>
---
 drivers/clk/rockchip/clk_pll.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/rockchip/clk_pll.c b/drivers/clk/rockchip/clk_pll.c
index c6fbeb71c77a..6324c11091af 100644
--- a/drivers/clk/rockchip/clk_pll.c
+++ b/drivers/clk/rockchip/clk_pll.c
@@ -168,16 +168,21 @@ rockchip_pll_clk_set_by_auto(ulong fin_hz,
 }
 
 static s16
-rockchip_rk3588_pll_k_get(u32 m, u32 p, u32 s, u64 fin_hz, u64 fvco)
+rockchip_rk3588_pll_k_get(u32 *m, u32 p, u32 s, u64 fin_hz, u64 fvco)
 {
 	u64 fref, ffrac;
 	int k;
 
 	fref = fin_hz / p;
-	ffrac = fvco - (m * fref);
+	ffrac = fvco - (*m) * fref;
 	k = ffrac * 65536 / fref;
 	if (k > 32767) {
-		ffrac = ((m + 1) * fref) - fvco;
+		/*
+		 * The requested rate is closer to the next integer multiplier
+		 * m, so pick it and use a negative fractional coefficient k
+		 */
+		*m += 1;
+		ffrac = (*m) * fref - fvco;
 		/*
 		 * Round up to avoid overshooting requested rate for negative k
 		 */
@@ -201,7 +206,10 @@ rockchip_rk3588_pll_frac_by_auto(unsigned long fin_hz, unsigned long fout_hz)
 			for (m = 64; m <= 1023; m++) {
 				if ((fvco >= m * fin_hz / p) &&
 				    (fvco < (m + 1) * fin_hz / p)) {
-					k = rockchip_rk3588_pll_k_get(m, p, s,
+					u32 m_tmp = m;
+
+					k = rockchip_rk3588_pll_k_get(&m_tmp,
+								      p, s,
 								      fin_hz,
 								      fvco);
 					if (!k)
@@ -209,10 +217,7 @@ rockchip_rk3588_pll_frac_by_auto(unsigned long fin_hz, unsigned long fout_hz)
 					rate_table->p = p;
 					rate_table->s = s;
 					rate_table->k = k;
-					if (k > 32767)
-						rate_table->m = m + 1;
-					else
-						rate_table->m = m;
+					rate_table->m = m_tmp;
 					return rate_table;
 				}
 			}

-- 
2.53.0