[v2] dmaengine: mv_xor_v2: Fix -Wshift-negative-value
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Message ID 20190813173448.109859-1-nhuck@google.com
State Accepted
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Series
  • [v2] dmaengine: mv_xor_v2: Fix -Wshift-negative-value
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Commit Message

Nathan Huckleberry Aug. 13, 2019, 5:34 p.m. UTC
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>
---
 drivers/dma/mv_xor_v2.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

Comments

Nick Desaulniers Aug. 13, 2019, 8:43 p.m. UTC | #1
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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Vinod Koul Aug. 20, 2019, 11:36 a.m. UTC | #2
On 13-08-19, 10:34, Nathan Huckleberry 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.

Applied, thanks

Patch
diff mbox series

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);
 }