[PATCH] clk: imx: fix integer overflow in AV PLL round rate

[PATCH] clk: imx: fix integer overflow in AV PLL round rate

[Fabio Estevam]

From: Emil Lundmark <emil@limesaudio.com>

[commit 5c2f117a22e46a4afee6ddee29b653a7a2a6b41f upstream]

Since 'parent_rate * mfn' may overflow 32 bits, the result should be
stored using 64 bits.

The problem was discovered when trying to set the rate of the audio PLL
(pll4_post_div) on an i.MX6Q. The desired rate was 196.608 MHz, but
the actual rate returned was 192.000570 MHz. The round rate function should
have been able to return 196.608 MHz, i.e., the desired rate.

Cc: <stable@vger.kernel.org> # 4.8.x
Fixes: ba7f4f557eb6 ("clk: imx: correct AV PLL rate formula")
Cc: Anson Huang <b20788@freescale.com>
Signed-off-by: Emil Lundmark <emil@limesaudio.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
---
 drivers/clk/imx/clk-pllv3.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/imx/clk-pllv3.c b/drivers/clk/imx/clk-pllv3.c
index 19f9b62..7a6acc3 100644
--- a/drivers/clk/imx/clk-pllv3.c
+++ b/drivers/clk/imx/clk-pllv3.c
@@ -223,7 +223,7 @@ static unsigned long clk_pllv3_av_recalc_rate(struct clk_hw *hw,
 	temp64 *= mfn;
 	do_div(temp64, mfd);
 
-	return (parent_rate * div) + (u32)temp64;
+	return parent_rate * div + (unsigned long)temp64;
 }
 
 static long clk_pllv3_av_round_rate(struct clk_hw *hw, unsigned long rate,
@@ -247,7 +247,11 @@ static long clk_pllv3_av_round_rate(struct clk_hw *hw, unsigned long rate,
 	do_div(temp64, parent_rate);
 	mfn = temp64;
 
-	return parent_rate * div + parent_rate * mfn / mfd;
+	temp64 = (u64)parent_rate;
+	temp64 *= mfn;
+	do_div(temp64, mfd);
+
+	return parent_rate * div + (unsigned long)temp64;
 }
 
 static int clk_pllv3_av_set_rate(struct clk_hw *hw, unsigned long rate,
-- 
2.7.4