linux-kernel - drivers/clk/sophgo/clk-sg2042-pll.c:217:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64

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Message-ID: <202410242248.o7XIZVqz-lkp@intel.com>
Date: Thu, 24 Oct 2024 22:49:12 +0800
From: kernel test robot <lkp@...el.com>
To: Chen Wang <unicorn_wang@...look.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: drivers/clk/sophgo/clk-sg2042-pll.c:217:1-7: WARNING: do_div() does
 a 64-by-32 division, please consider using div64_ul instead.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   c2ee9f594da826bea183ed14f2cc029c719bf4da
commit: 48cf7e01386e7e35ea12255bc401bdd484c34e7d clk: sophgo: Add SG2042 clock driver
date:   4 months ago
config: loongarch-randconfig-r054-20241024 (https://download.01.org/0day-ci/archive/20241024/202410242248.o7XIZVqz-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 14.1.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410242248.o7XIZVqz-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> drivers/clk/sophgo/clk-sg2042-pll.c:217:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_ul instead.
>> drivers/clk/sophgo/clk-sg2042-pll.c:160:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead.

vim +217 drivers/clk/sophgo/clk-sg2042-pll.c

   138	
   139	/**
   140	 * sg2042_pll_recalc_rate() - Calculate rate for plls
   141	 * @reg_value: current register value
   142	 * @parent_rate: parent frequency
   143	 *
   144	 * This function is used to calculate below "rate" in equation
   145	 * rate = (parent_rate/REFDIV) x FBDIV/POSTDIV1/POSTDIV2
   146	 *      = (parent_rate x FBDIV) / (REFDIV x POSTDIV1 x POSTDIV2)
   147	 *
   148	 * Return: The rate calculated.
   149	 */
   150	static unsigned long sg2042_pll_recalc_rate(unsigned int reg_value,
   151						    unsigned long parent_rate)
   152	{
   153		struct sg2042_pll_ctrl ctrl_table;
   154		u64 numerator, denominator;
   155	
   156		sg2042_pll_ctrl_decode(reg_value, &ctrl_table);
   157	
   158		numerator = parent_rate * ctrl_table.fbdiv;
   159		denominator = ctrl_table.refdiv * ctrl_table.postdiv1 * ctrl_table.postdiv2;
 > 160		do_div(numerator, denominator);
   161		return numerator;
   162	}
   163	
   164	/**
   165	 * sg2042_pll_get_postdiv_1_2() - Based on input rate/prate/fbdiv/refdiv,
   166	 * look up the postdiv1_2 table to get the closest postdiiv combination.
   167	 * @rate: FOUTPOSTDIV
   168	 * @prate: parent rate, i.e. FREF
   169	 * @fbdiv: FBDIV
   170	 * @refdiv: REFDIV
   171	 * @postdiv1: POSTDIV1, output
   172	 * @postdiv2: POSTDIV2, output
   173	 *
   174	 * postdiv1_2 contains all the possible combination lists of POSTDIV1 and POSTDIV2
   175	 * for example:
   176	 * postdiv1_2[0] = {2, 4, 8}, where div1 = 2, div2 = 4 , div1 * div2 = 8
   177	 *
   178	 * See TRM:
   179	 * FOUTPOSTDIV = FREF * FBDIV / REFDIV / (POSTDIV1 * POSTDIV2)
   180	 * So we get following formula to get POSTDIV1 and POSTDIV2:
   181	 * POSTDIV = (prate/REFDIV) x FBDIV/rate
   182	 * above POSTDIV = POSTDIV1*POSTDIV2
   183	 *
   184	 * Return:
   185	 * %0 - OK
   186	 * %-EINVAL - invalid argument, which means Failed to get the postdivs.
   187	 */
   188	static int sg2042_pll_get_postdiv_1_2(unsigned long rate,
   189					      unsigned long prate,
   190					      unsigned int fbdiv,
   191					      unsigned int refdiv,
   192					      unsigned int *postdiv1,
   193					      unsigned int *postdiv2)
   194	{
   195		int index;
   196		u64 tmp0;
   197	
   198		/* POSTDIV_RESULT_INDEX point to 3rd element in the array postdiv1_2 */
   199		#define	POSTDIV_RESULT_INDEX	2
   200	
   201		static const int postdiv1_2[][3] = {
   202			{2, 4,  8}, {3, 3,  9}, {2, 5, 10}, {2, 6, 12},
   203			{2, 7, 14}, {3, 5, 15}, {4, 4, 16}, {3, 6, 18},
   204			{4, 5, 20}, {3, 7, 21}, {4, 6, 24}, {5, 5, 25},
   205			{4, 7, 28}, {5, 6, 30}, {5, 7, 35}, {6, 6, 36},
   206			{6, 7, 42}, {7, 7, 49}
   207		};
   208	
   209		/* prate/REFDIV and result save to tmp0 */
   210		tmp0 = prate;
   211		do_div(tmp0, refdiv);
   212	
   213		/* ((prate/REFDIV) x FBDIV) and result save to tmp0 */
   214		tmp0 *= fbdiv;
   215	
   216		/* ((prate/REFDIV) x FBDIV)/rate and result save to tmp0 */
 > 217		do_div(tmp0, rate);
   218	
   219		/* tmp0 is POSTDIV1*POSTDIV2, now we calculate div1 and div2 value */
   220		if (tmp0 <= 7) {
   221			/* (div1 * div2) <= 7, no need to use array search */
   222			*postdiv1 = tmp0;
   223			*postdiv2 = 1;
   224			return 0;
   225		}
   226	
   227		/* (div1 * div2) > 7, use array search */
   228		for (index = 0; index < ARRAY_SIZE(postdiv1_2); index++) {
   229			if (tmp0 > postdiv1_2[index][POSTDIV_RESULT_INDEX]) {
   230				continue;
   231			} else {
   232				/* found it */
   233				*postdiv1 = postdiv1_2[index][1];
   234				*postdiv2 = postdiv1_2[index][0];
   235				return 0;
   236			}
   237		}
   238		pr_warn("%s can not find in postdiv array!\n", __func__);
   239		return -EINVAL;
   240	}
   241	

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