From c2910c00fee4cbb7b222d6e02846adef9ae4135a Mon Sep 17 00:00:00 2001
From: Claudiu Beznea <claudiu.beznea@microchip.com>
Date: Mon, 11 Oct 2021 14:27:12 +0300
Subject: [PATCH] clk: at91: clk-master: check if div or pres is zero
Git-commit: c2910c00fee4cbb7b222d6e02846adef9ae4135a
Patch-mainline: v5.16-rc1
References: git-fixes stable-5.14.19

Check if div or pres is zero before using it as argument for ffs().
In case div is zero ffs() will return 0 and thus substracting from
zero will lead to invalid values to be setup in registers.

Fixes: 7a110b9107ed8 ("clk: at91: clk-master: re-factor master clock")
Fixes: 75c88143f3b87 ("clk: at91: clk-master: add master clock support for SAMA7G5")
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20211011112719.3951784-9-claudiu.beznea@microchip.com
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/clk/at91/clk-master.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/at91/clk-master.c b/drivers/clk/at91/clk-master.c
index 9a2c8e64cacf..2093e13b5068 100644
--- a/drivers/clk/at91/clk-master.c
+++ b/drivers/clk/at91/clk-master.c
@@ -344,7 +344,7 @@ static int clk_master_pres_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	else if (pres == 3)
 		pres = MASTER_PRES_MAX;
-	else
+	else if (pres)
 		pres = ffs(pres) - 1;
 
 	spin_lock_irqsave(master->lock, flags);
@@ -757,7 +757,7 @@ static int clk_sama7g5_master_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	if (div == 3)
 		div = MASTER_PRES_MAX;
-	else
+	else if (div)
 		div = ffs(div) - 1;
 
 	spin_lock_irqsave(master->lock, flags);
-- 
2.26.2