From 79a3e118b016bf6a64a5e52ca32ecc2e2c1def0f Mon Sep 17 00:00:00 2001
From: Ronald Wahl <rwahl@gmx.de>
Date: Wed, 10 Oct 2018 15:54:54 +0200
Subject: [PATCH] clk: at91: Fix division by zero in PLL recalc_rate()

commit 0f5cb0e6225cae2f029944cb8c74617aab6ddd49 upstream.

Commit a982e45dc150 ("clk: at91: PLL recalc_rate() now using cached MUL
and DIV values") removed a check that prevents a division by zero. This
now causes a stacktrace when booting the kernel on a at91 platform if
the PLL DIV register contains zero. This commit reintroduces this check.

Fixes: a982e45dc150 ("clk: at91: PLL recalc_rate() now using cached...")
Cc: <stable@vger.kernel.org>
Signed-off-by: Ronald Wahl <rwahl@gmx.de>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/clk/at91/clk-pll.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/clk/at91/clk-pll.c b/drivers/clk/at91/clk-pll.c
index 2bb2551c6245..a17a428fa706 100644
--- a/drivers/clk/at91/clk-pll.c
+++ b/drivers/clk/at91/clk-pll.c
@@ -133,6 +133,9 @@ static unsigned long clk_pll_recalc_rate(struct clk_hw *hw,
 {
 	struct clk_pll *pll = to_clk_pll(hw);
 
+	if (!pll->div || !pll->mul)
+		return 0;
+
 	return (parent_rate / pll->div) * (pll->mul + 1);
 }