Re: [PATCH] i2c: altera: Use 64-bit arithmetic instead of 32-bit

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On 2/10/20 1:26 PM, Gustavo A. R. Silva wrote:
Add suffix ULL to constant 300 in order to avoid a potential integer
overflow and give the compiler complete information about the proper
arithmetic to use. Notice that this constant is being used in a context
that expects an expression of type u64, but it's currently evaluated
using 32-bit arithmetic.

Addresses-Coverity: 1458369 ("Unintentional integer overflow")
Fixes: 0560ad576268 ("i2c: altera: Add Altera I2C Controller driver")
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
---
  drivers/i2c/busses/i2c-altera.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-altera.c b/drivers/i2c/busses/i2c-altera.c
index 5255d3755411..526f453f0ff7 100644
--- a/drivers/i2c/busses/i2c-altera.c
+++ b/drivers/i2c/busses/i2c-altera.c
@@ -171,7 +171,8 @@ static void altr_i2c_init(struct altr_i2c_dev *idev)
  	/* 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(div_u64(300ULL * clk_mhz, 1000),
+	       idev->base + ALTR_I2C_SDA_HOLD);
/* Mask all master interrupt bits */
  	altr_i2c_int_enable(idev, ALTR_I2C_ALL_IRQ, false);

Thank you.

Reviewed-by: Thor Thayer <thor.thayer@xxxxxxxxxxxxxxx>



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