linux-kernel - [PATCH v2] dmaengine: mv_xor_v2: Fix -Wshift-negative-value

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Message-Id: <20190813173448.109859-1-nhuck@google.com>
Date:   Tue, 13 Aug 2019 10:34:48 -0700
From:   Nathan Huckleberry <nhuck@...gle.com>
To:     dan.j.williams@...el.com, vkoul@...nel.org
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Huckleberry <nhuck@...gle.com>,
        clang-built-linux@...glegroups.com
Subject: [PATCH v2] dmaengine: mv_xor_v2: Fix -Wshift-negative-value

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@...glegroups.com
Link: https://github.com/ClangBuiltLinux/linux/issues/521
Signed-off-by: Nathan Huckleberry <nhuck@...gle.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