clk: at91: usb: fix at91sam9x5 recalc, round and set rate

commit 69daf75a upstream.

First check for rate == 0 in set_rate and round_rate to avoid div by zero.
Then, in order to get the closest rate, round all divisions to the closest
result instead of rounding them down.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>
[ luis: 3.16 prereq for:
  45912431 "clk: at91: usb: propagate rate modification to the parent clk" ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/clk/at91/clk-usb.c

@@ -52,29 +52,26 @@ static unsigned long at91sam9x5_clk_usb_recalc_rate(struct clk_hw *hw,
 
 	tmp = pmc_read(pmc, AT91_PMC_USB);
 	usbdiv = (tmp & AT91_PMC_OHCIUSBDIV) >> SAM9X5_USB_DIV_SHIFT;
-	return parent_rate / (usbdiv + 1);
+
+	return DIV_ROUND_CLOSEST(parent_rate, (usbdiv + 1));
 }
 
 static long at91sam9x5_clk_usb_round_rate(struct clk_hw *hw, unsigned long rate,
 					  unsigned long *parent_rate)
 {
 	unsigned long div;
-	unsigned long bestrate;
-	unsigned long tmp;
+
+	if (!rate)
+		return -EINVAL;
 
 	if (rate >= *parent_rate)
 		return *parent_rate;
 
-	div = *parent_rate / rate;
-	if (div >= SAM9X5_USB_MAX_DIV)
-		return *parent_rate / (SAM9X5_USB_MAX_DIV + 1);
+	div = DIV_ROUND_CLOSEST(*parent_rate, rate);
+	if (div > SAM9X5_USB_MAX_DIV + 1)
+		div = SAM9X5_USB_MAX_DIV + 1;
 
-	bestrate = *parent_rate / div;
-	tmp = *parent_rate / (div + 1);
-	if (bestrate - rate > rate - tmp)
-		bestrate = tmp;
-
-	return bestrate;
+	return DIV_ROUND_CLOSEST(*parent_rate, div);
 }
 
 static int at91sam9x5_clk_usb_set_parent(struct clk_hw *hw, u8 index)
@@ -106,9 +103,13 @@ static int at91sam9x5_clk_usb_set_rate(struct clk_hw *hw, unsigned long rate,
 	u32 tmp;
 	struct at91sam9x5_clk_usb *usb = to_at91sam9x5_clk_usb(hw);
 	struct at91_pmc *pmc = usb->pmc;
-	unsigned long div = parent_rate / rate;
+	unsigned long div;
+
+	if (!rate)
+		return -EINVAL;
 
-	if (parent_rate % rate || div < 1 || div >= SAM9X5_USB_MAX_DIV)
+	div = DIV_ROUND_CLOSEST(parent_rate, rate);
+	if (div > SAM9X5_USB_MAX_DIV + 1 || !div)
 		return -EINVAL;
 
 	tmp = pmc_read(pmc, AT91_PMC_USB) & ~AT91_PMC_OHCIUSBDIV;