linux-kernel - drivers/media/i2c/tc358746.c:817:13: warning: 'p

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Date:   Fri, 24 Feb 2023 09:10:32 +0800
From:   kernel test robot <lkp@...el.com>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: drivers/media/i2c/tc358746.c:817:13: warning: 'p_best' is used
 uninitialized

Hi Marco,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   e4bc15889506723d7b93c053ad4a75cd58248d74
commit: 80a21da360516fa602f3a50eb9792f9dfbfb5fdb media: tc358746: add Toshiba TC358746 Parallel to CSI-2 bridge driver
date:   4 months ago
config: arc-randconfig-r031-20230223 (https://download.01.org/0day-ci/archive/20230224/202302240951.roaFGUy5-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 12.1.0
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
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=80a21da360516fa602f3a50eb9792f9dfbfb5fdb
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 80a21da360516fa602f3a50eb9792f9dfbfb5fdb
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash drivers/media/i2c/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202302240951.roaFGUy5-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/media/i2c/tc358746.c: In function 'tc358746_find_pll_settings':
>> drivers/media/i2c/tc358746.c:817:13: warning: 'p_best' is used uninitialized [-Wuninitialized]
     817 |         u16 p_best, p;
         |             ^~~~~~
>> drivers/media/i2c/tc358746.c:816:13: warning: 'm_best' is used uninitialized [-Wuninitialized]
     816 |         u16 m_best, mul;
         |             ^~~~~~


vim +/p_best +817 drivers/media/i2c/tc358746.c

   805	
   806	static unsigned long tc358746_find_pll_settings(struct tc358746 *tc358746,
   807							unsigned long refclk,
   808							unsigned long fout)
   809	
   810	{
   811		struct device *dev = tc358746->sd.dev;
   812		unsigned long best_freq = 0;
   813		u32 min_delta = 0xffffffff;
   814		u16 prediv_max = 17;
   815		u16 prediv_min = 1;
 > 816		u16 m_best, mul;
 > 817		u16 p_best, p;
   818		u8 postdiv;
   819	
   820		if (fout > 1000 * HZ_PER_MHZ) {
   821			dev_err(dev, "HS-Clock above 1 Ghz are not supported\n");
   822			return 0;
   823		}
   824	
   825		if (fout >= 500 * HZ_PER_MHZ)
   826			postdiv = 1;
   827		else if (fout >= 250 * HZ_PER_MHZ)
   828			postdiv = 2;
   829		else if (fout >= 125 * HZ_PER_MHZ)
   830			postdiv = 4;
   831		else
   832			postdiv = 8;
   833	
   834		for (p = prediv_min; p <= prediv_max; p++) {
   835			unsigned long delta, fin;
   836			u64 tmp;
   837	
   838			fin = DIV_ROUND_CLOSEST(refclk, p);
   839			if (fin < 4 * HZ_PER_MHZ || fin > 40 * HZ_PER_MHZ)
   840				continue;
   841	
   842			tmp = fout * p * postdiv;
   843			do_div(tmp, fin);
   844			mul = tmp;
   845			if (mul > 511)
   846				continue;
   847	
   848			tmp = mul * fin;
   849			do_div(tmp, p * postdiv);
   850	
   851			delta = abs(fout - tmp);
   852			if (delta < min_delta) {
   853				p_best = p;
   854				m_best = mul;
   855				min_delta = delta;
   856				best_freq = tmp;
   857			};
   858	
   859			if (delta == 0)
   860				break;
   861		};
   862	
   863		if (!best_freq) {
   864			dev_err(dev, "Failed find PLL frequency\n");
   865			return 0;
   866		}
   867	
   868		tc358746->pll_post_div = postdiv;
   869		tc358746->pll_pre_div = p_best;
   870		tc358746->pll_mul = m_best;
   871	
   872		if (best_freq != fout)
   873			dev_warn(dev, "Request PLL freq:%lu, found PLL freq:%lu\n",
   874				 fout, best_freq);
   875	
   876		dev_dbg(dev, "Found PLL settings: freq:%lu prediv:%u multi:%u postdiv:%u\n",
   877			best_freq, p_best, m_best, postdiv);
   878	
   879		return best_freq;
   880	}
   881	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests