arch/arm/mach-ep93xx/clock.c:210:35: sparse: sparse: Using plain integer as NULL pointer

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   4d66020dcef83314092f2c8c89152a8d122627e2
commit: 9645ccc7bd7a16cd73c3be9dee70cd702b03be37 ep93xx: clock: convert in-place to COMMON_CLK
date:   3 months ago
config: arm-randconfig-s031-20220116 (https://download.01.org/0day-ci/archive/20220117/202201170148.vIvPQRko-lkp@xxxxxxxxx/config)
compiler: arm-linux-gnueabi-gcc (GCC) 11.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.4-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9645ccc7bd7a16cd73c3be9dee70cd702b03be37
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 9645ccc7bd7a16cd73c3be9dee70cd702b03be37
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=arm SHELL=/bin/bash

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


sparse warnings: (new ones prefixed by >>)
>> arch/arm/mach-ep93xx/clock.c:210:35: sparse: sparse: Using plain integer as NULL pointer
   arch/arm/mach-ep93xx/clock.c:99:9: sparse: sparse: context imbalance in 'ep93xx_clk_enable' - different lock contexts for basic block
   arch/arm/mach-ep93xx/clock.c:116:9: sparse: sparse: context imbalance in 'ep93xx_clk_disable' - different lock contexts for basic block
   arch/arm/mach-ep93xx/clock.c:197:9: sparse: sparse: context imbalance in 'ep93xx_mux_set_parent_lock' - different lock contexts for basic block

vim +210 arch/arm/mach-ep93xx/clock.c

   205	
   206	static int ep93xx_mux_determine_rate(struct clk_hw *hw,
   207					struct clk_rate_request *req)
   208	{
   209		unsigned long rate = req->rate;
 > 210		struct clk *best_parent = 0;
   211		unsigned long __parent_rate;
   212		unsigned long best_rate = 0, actual_rate, mclk_rate;
   213		unsigned long best_parent_rate;
   214		int __div = 0, __pdiv = 0;
   215		int i;
   216	
   217		/*
   218		 * Try the two pll's and the external clock
   219		 * Because the valid predividers are 2, 2.5 and 3, we multiply
   220		 * all the clocks by 2 to avoid floating point math.
   221		 *
   222		 * This is based on the algorithm in the ep93xx raster guide:
   223		 * http://be-a-maverick.com/en/pubs/appNote/AN269REV1.pdf
   224		 *
   225		 */
   226		for (i = 0; i < ARRAY_SIZE(mux_parents); i++) {
   227			struct clk *parent = clk_get_sys(mux_parents[i], NULL);
   228	
   229			__parent_rate = clk_get_rate(parent);
   230			mclk_rate = __parent_rate * 2;
   231	
   232			/* Try each predivider value */
   233			for (__pdiv = 4; __pdiv <= 6; __pdiv++) {
   234				__div = mclk_rate / (rate * __pdiv);
   235				if (__div < 2 || __div > 127)
   236					continue;
   237	
   238				actual_rate = mclk_rate / (__pdiv * __div);
   239				if (is_best(rate, actual_rate, best_rate)) {
   240					best_rate = actual_rate;
   241					best_parent_rate = __parent_rate;
   242					best_parent = parent;
   243				}
   244			}
   245		}
   246	
   247		if (!best_parent)
   248			return -EINVAL;
   249	
   250		req->best_parent_rate = best_parent_rate;
   251		req->best_parent_hw = __clk_get_hw(best_parent);
   252		req->rate = best_rate;
   253	
   254		return 0;
   255	}
   256	

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