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SubjectRe: [PATCH v2] dmaengine: mv_xor_v2: Fix -Wshift-negative-value
On Tue, Aug 13, 2019 at 10:35 AM 'Nathan Huckleberry' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
>
> Clang produces the following warning
>
> drivers/dma/mv_xor_v2.c:264:40: warning: shifting a negative signed value
> is undefined [-Wshift-negative-value]
> reg &= (~MV_XOR_V2_DMA_IMSG_THRD_MASK <<
> MV_XOR_V2_DMA_IMSG_THRD_SHIFT);
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
> drivers/dma/mv_xor_v2.c:271:46: warning: shifting a negative signed value
> is undefined [-Wshift-negative-value]
> reg &= (~MV_XOR_V2_DMA_IMSG_TIMER_THRD_MASK <<
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
>
> Upon further investigation MV_XOR_V2_DMA_IMSG_THRD_SHIFT and
> MV_XOR_V2_DMA_IMSG_TIMER_THRD_SHIFT are both 0. Since shifting by 0 does
> nothing, these variables can be removed.
>
> Cc: clang-built-linux@googlegroups.com
> Link: https://github.com/ClangBuiltLinux/linux/issues/521
> Signed-off-by: Nathan Huckleberry <nhuck@google.com>

Thanks for sending a v2:
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
> drivers/dma/mv_xor_v2.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/dma/mv_xor_v2.c b/drivers/dma/mv_xor_v2.c
> index fa5dab481203..e3850f04f676 100644
> --- a/drivers/dma/mv_xor_v2.c
> +++ b/drivers/dma/mv_xor_v2.c
> @@ -33,7 +33,6 @@
> #define MV_XOR_V2_DMA_IMSG_CDAT_OFF 0x014
> #define MV_XOR_V2_DMA_IMSG_THRD_OFF 0x018
> #define MV_XOR_V2_DMA_IMSG_THRD_MASK 0x7FFF
> -#define MV_XOR_V2_DMA_IMSG_THRD_SHIFT 0x0
> #define MV_XOR_V2_DMA_IMSG_TIMER_EN BIT(18)
> #define MV_XOR_V2_DMA_DESQ_AWATTR_OFF 0x01C
> /* Same flags as MV_XOR_V2_DMA_DESQ_ARATTR_OFF */
> @@ -50,7 +49,6 @@
> #define MV_XOR_V2_DMA_DESQ_ADD_OFF 0x808
> #define MV_XOR_V2_DMA_IMSG_TMOT 0x810
> #define MV_XOR_V2_DMA_IMSG_TIMER_THRD_MASK 0x1FFF
> -#define MV_XOR_V2_DMA_IMSG_TIMER_THRD_SHIFT 0
>
> /* XOR Global registers */
> #define MV_XOR_V2_GLOB_BW_CTRL 0x4
> @@ -261,16 +259,15 @@ void mv_xor_v2_enable_imsg_thrd(struct mv_xor_v2_device *xor_dev)
>
> /* Configure threshold of number of descriptors, and enable timer */
> reg = readl(xor_dev->dma_base + MV_XOR_V2_DMA_IMSG_THRD_OFF);
> - reg &= (~MV_XOR_V2_DMA_IMSG_THRD_MASK << MV_XOR_V2_DMA_IMSG_THRD_SHIFT);
> - reg |= (MV_XOR_V2_DONE_IMSG_THRD << MV_XOR_V2_DMA_IMSG_THRD_SHIFT);
> + reg &= ~MV_XOR_V2_DMA_IMSG_THRD_MASK;
> + reg |= MV_XOR_V2_DONE_IMSG_THRD;
> reg |= MV_XOR_V2_DMA_IMSG_TIMER_EN;
> writel(reg, xor_dev->dma_base + MV_XOR_V2_DMA_IMSG_THRD_OFF);
>
> /* Configure Timer Threshold */
> reg = readl(xor_dev->dma_base + MV_XOR_V2_DMA_IMSG_TMOT);
> - reg &= (~MV_XOR_V2_DMA_IMSG_TIMER_THRD_MASK <<
> - MV_XOR_V2_DMA_IMSG_TIMER_THRD_SHIFT);
> - reg |= (MV_XOR_V2_TIMER_THRD << MV_XOR_V2_DMA_IMSG_TIMER_THRD_SHIFT);
> + reg &= ~MV_XOR_V2_DMA_IMSG_TIMER_THRD_MASK;
> + reg |= MV_XOR_V2_TIMER_THRD;
> writel(reg, xor_dev->dma_base + MV_XOR_V2_DMA_IMSG_TMOT);
> }
>
> --
> 2.23.0.rc1.153.gdeed80330f-goog
>
> --
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--
Thanks,
~Nick Desaulniers

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