linux-kernel - [PATCH 5.4 095/152] i2c: altera: Fix potential integer overflow

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Date:   Tue,  3 Mar 2020 18:43:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Laight <David.Laight@...LAB.COM>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Thor Thayer <thor.thayer@...ux.intel.com>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: [PATCH 5.4 095/152] i2c: altera: Fix potential integer overflow

From: Gustavo A. R. Silva <gustavo@...eddedor.com>

commit 54498e8070e19e74498a72c7331348143e7e1f8c upstream.

Factor out 100 from the equation and do 32-bit arithmetic (3 * clk_mhz / 10)
instead of 64-bit.

Notice that clk_mhz is MHz, so the multiplication will never wrap 32 bits
and there is no need for div_u64().

Addresses-Coverity: 1458369 ("Unintentional integer overflow")
Fixes: 0560ad576268 ("i2c: altera: Add Altera I2C Controller driver")
Suggested-by: David Laight <David.Laight@...LAB.COM>
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
Reviewed-by: Thor Thayer <thor.thayer@...ux.intel.com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/i2c/busses/i2c-altera.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/i2c/busses/i2c-altera.c
+++ b/drivers/i2c/busses/i2c-altera.c
@@ -171,7 +171,7 @@ static void altr_i2c_init(struct altr_i2
 	/* SCL Low Time */
 	writel(t_low, idev->base + ALTR_I2C_SCL_LOW);
 	/* SDA Hold Time, 300ns */
-	writel(div_u64(300 * clk_mhz, 1000), idev->base + ALTR_I2C_SDA_HOLD);
+	writel(3 * clk_mhz / 10, idev->base + ALTR_I2C_SDA_HOLD);
 
 	/* Mask all master interrupt bits */
 	altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);