linux-kernel - [nbd168-wireless:mt76 5/28] drivers/net/wireless/mediatek/mt76/mt7915/dma.c:97:6: warning: variable 'base' is used uninitialized whenever 'if' condition is false

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Message-ID: <202112230704.dKCp3lmX-lkp@intel.com>
Date:   Thu, 23 Dec 2021 07:25:34 +0800
From:   kernel test robot <lkp@...el.com>
To:     Bo Jiao <Bo.Jiao@...iatek.com>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Felix Fietkau <nbd@....name>,
        Sujuan Chen <sujuan.chen@...iatek.com>,
        Ryder Lee <ryder.lee@...iatek.com>
Subject: [nbd168-wireless:mt76 5/28]
 drivers/net/wireless/mediatek/mt76/mt7915/dma.c:97:6: warning: variable
 'base' is used uninitialized whenever 'if' condition is false

tree:   https://github.com/nbd168/wireless mt76
head:   05f0500c7b0147353e97de7369d504c5fbd3951e
commit: 22c2fb9495d35e0c442c23bcd3b8a4a18a28c62d [5/28] mt76: mt7915: rework dma.c to adapt mt7916 changes
config: mips-randconfig-r033-20211222 (https://download.01.org/0day-ci/archive/20211223/202112230704.dKCp3lmX-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project de4e0195ae1c39f1c3b07834b8e32c113f4f20eb)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install mips cross compiling tool for clang build
        # apt-get install binutils-mips-linux-gnu
        # https://github.com/nbd168/wireless/commit/22c2fb9495d35e0c442c23bcd3b8a4a18a28c62d
        git remote add nbd168-wireless https://github.com/nbd168/wireless
        git fetch --no-tags nbd168-wireless mt76
        git checkout 22c2fb9495d35e0c442c23bcd3b8a4a18a28c62d
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash drivers/net/wireless/mediatek/mt76/mt7915/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> drivers/net/wireless/mediatek/mt76/mt7915/dma.c:97:6: warning: variable 'base' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           if (!is_mt7915(&dev->mt76)) {
               ^~~~~~~~~~~~~~~~~~~~~~
   drivers/net/wireless/mediatek/mt76/mt7915/dma.c:101:70: note: uninitialized use occurs here
           mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_EXT_WA) + ofs, PREFETCH(0x1c0 + base, 0x4));
                                                                               ^~~~
   drivers/net/wireless/mediatek/mt76/mt7915/dma.c:85:35: note: expanded from macro 'PREFETCH'
   #define PREFETCH(_base, _depth) ((_base) << 16 | (_depth))
                                     ^~~~~
   drivers/net/wireless/mediatek/mt76/mt7915/../mt76.h:829:63: note: expanded from macro 'mt76_wr'
   #define mt76_wr(dev, ...)       (dev)->mt76.bus->wr(&((dev)->mt76), __VA_ARGS__)
                                                                       ^~~~~~~~~~~
   drivers/net/wireless/mediatek/mt76/mt7915/dma.c:97:2: note: remove the 'if' if its condition is always true
           if (!is_mt7915(&dev->mt76)) {
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/net/wireless/mediatek/mt76/mt7915/dma.c:86:10: note: initialize the variable 'base' to silence this warning
           u32 base;
                   ^
                    = 0
   1 warning generated.


vim +97 drivers/net/wireless/mediatek/mt76/mt7915/dma.c

    82	
    83	static void __mt7915_dma_prefetch(struct mt7915_dev *dev, u32 ofs)
    84	{
    85	#define PREFETCH(_base, _depth)	((_base) << 16 | (_depth))
    86		u32 base;
    87	
    88		/* prefetch SRAM wrapping boundary for tx/rx ring. */
    89		mt76_wr(dev, MT_MCUQ_EXT_CTRL(MT_MCUQ_FWDL) + ofs, PREFETCH(0x0, 0x4));
    90		mt76_wr(dev, MT_MCUQ_EXT_CTRL(MT_MCUQ_WM) + ofs, PREFETCH(0x40, 0x4));
    91		mt76_wr(dev, MT_TXQ_EXT_CTRL(0) + ofs, PREFETCH(0x80, 0x4));
    92		mt76_wr(dev, MT_TXQ_EXT_CTRL(1) + ofs, PREFETCH(0xc0, 0x4));
    93		mt76_wr(dev, MT_MCUQ_EXT_CTRL(MT_MCUQ_WA) + ofs, PREFETCH(0x100, 0x4));
    94	
    95		mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_MCU) + ofs, PREFETCH(0x140, 0x4));
    96		mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_MCU_WA) + ofs, PREFETCH(0x180, 0x4));
  > 97		if (!is_mt7915(&dev->mt76)) {
    98			mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_MAIN_WA) + ofs, PREFETCH(0x1c0, 0x4));
    99			base = 0x40;
   100		}
   101		mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_EXT_WA) + ofs, PREFETCH(0x1c0 + base, 0x4));
   102		mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_MAIN) + ofs, PREFETCH(0x200 + base, 0x4));
   103		mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_EXT) + ofs, PREFETCH(0x240 + base, 0x4));
   104	
   105		/* for mt7915, the ring which is next the last
   106		 * used ring must be initialized.
   107		 */
   108		if (is_mt7915(&dev->mt76)) {
   109			ofs += 0x4;
   110			mt76_wr(dev, MT_MCUQ_EXT_CTRL(MT_MCUQ_WA) + ofs, PREFETCH(0x140, 0x0));
   111			mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_EXT_WA) + ofs, PREFETCH(0x200 + base, 0x0));
   112			mt76_wr(dev, MT_RXQ_EXT_CTRL(MT_RXQ_EXT) + ofs, PREFETCH(0x280 + base, 0x0));
   113		}
   114	}
   115	

---
0-DAY CI Kernel Test Service, Intel Corporation
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