| Message ID | 20200210192656.GA8412@embeddedor |
|---|---|
| State | Superseded |
| Headers | show |
| Series | i2c: altera: Use 64-bit arithmetic instead of 32-bit | expand |
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@embeddedor.com> > --- > 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@linux.intel.com>
From: Gustavo A. R. Silva > Sent: 10 February 2020 19:27 > > 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@embeddedor.com> > --- > 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); Why not factor out the 100? It may then be you can do 32bit arithmetic (3 * clk_mhz / 10). If clk_mhz is MHz (not mHz) then the sum will never wrap 32 bits. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
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);
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@embeddedor.com> --- drivers/i2c/busses/i2c-altera.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)