clk: at91: optimization of the set_rate callback

Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/at91/clk-programmable.c

@@ -139,43 +139,21 @@ static int clk_programmable_set_rate(struct clk_hw *hw, unsigned long rate,
 	struct clk_programmable *prog = to_clk_programmable(hw);
 	struct at91_pmc *pmc = prog->pmc;
 	const struct clk_programmable_layout *layout = prog->layout;
-	unsigned long best_rate = parent_rate;
-	unsigned long best_diff;
-	unsigned long new_diff;
-	unsigned long cur_rate;
+	unsigned long div = parent_rate / rate;
 	int shift = 0;
 	u32 tmp = pmc_read(pmc, AT91_PMC_PCKR(prog->id)) &
 		  ~(PROG_PRES_MASK << layout->pres_shift);
 
-	if (rate > parent_rate)
-		return parent_rate;
-	else
-		best_diff = parent_rate - rate;
-
-	if (!best_diff) {
-		pmc_write(pmc, AT91_PMC_PCKR(prog->id), tmp | shift);
-		return 0;
-	}
-
-	for (shift = 1; shift < PROG_PRES_MASK; shift++) {
-		cur_rate = parent_rate >> shift;
-
-		if (cur_rate > rate)
-			new_diff = cur_rate - rate;
-		else
-			new_diff = rate - cur_rate;
+	if (!div)
+		return -EINVAL;
 
-		if (!new_diff)
-			break;
+	shift = fls(div) - 1;
 
-		if (new_diff < best_diff) {
-			best_diff = new_diff;
-			best_rate = cur_rate;
-		}
+	if (div != (1<<shift))
+		return -EINVAL;
 
-		if (rate > cur_rate)
-			break;
-	}
+	if (shift >= PROG_PRES_MASK)
+		return -EINVAL;
 
 	pmc_write(pmc, AT91_PMC_PCKR(prog->id),
 		  tmp | (shift << layout->pres_shift));