linux-kernel - drivers/phy/freescale/phy-fsl-samsung-hdmi.c:472:3-9: WARNING: do_div() does a 64-by-32 division, please consider using div64

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Message-ID: <202412091243.fSObwwPi-lkp@intel.com>
Date: Mon, 9 Dec 2024 13:08:47 +0800
From: kernel test robot <lkp@...el.com>
To: Adam Ford <aford173@...il.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Vinod Koul <vkoul@...nel.org>,
	Dominique Martinet <dominique.martinet@...ark-techno.com>,
	Frieder Schrempf <frieder.schrempf@...tron.de>
Subject: drivers/phy/freescale/phy-fsl-samsung-hdmi.c:472:3-9: 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:   fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
commit: 1951dbb41d1dff7c135eed4fa1a6330df6971549 phy: freescale: fsl-samsung-hdmi: Support dynamic integer
date:   8 weeks ago
config: alpha-randconfig-r064-20241209 (https://download.01.org/0day-ci/archive/20241209/202412091243.fSObwwPi-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 14.2.0

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/202412091243.fSObwwPi-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> drivers/phy/freescale/phy-fsl-samsung-hdmi.c:472:3-9: WARNING: do_div() does a 64-by-32 division, please consider using div64_ul instead.

vim +472 drivers/phy/freescale/phy-fsl-samsung-hdmi.c

   435	
   436	static unsigned long fsl_samsung_hdmi_phy_find_pms(unsigned long fout, u8 *p, u16 *m, u8 *s)
   437	{
   438		unsigned long best_freq = 0;
   439		u32 min_delta = 0xffffffff;
   440		u8 _p, best_p;
   441		u16 _m, best_m;
   442		u8 _s, best_s;
   443	
   444		/*
   445		 * Figure 13-78 of the reference manual states the PLL should be TMDS x 5
   446		 * while the TMDS_CLKO should be the PLL / 5.  So to calculate the PLL,
   447		 * take the pix clock x 5, then return the value of the PLL / 5.
   448		 */
   449		fout *= 5;
   450	
   451		/* The ref manual states the values of 'P' range from 1 to 11 */
   452		for (_p = 1; _p <= 11; ++_p) {
   453			for (_s = 1; _s <= 16; ++_s) {
   454				u64 tmp;
   455				u32 delta;
   456	
   457				/* s must be one or even */
   458				if (_s > 1 && (_s & 0x01) == 1)
   459					_s++;
   460	
   461				/* _s cannot be 14 per the TRM */
   462				if (_s == 14)
   463					continue;
   464	
   465				/*
   466				 * TODO: Ref Manual doesn't state the range of _m
   467				 * so this should be further refined if possible.
   468				 * This range was set based on the original values
   469				 * in the lookup table
   470				 */
   471				tmp = (u64)fout * (_p * _s);
 > 472				do_div(tmp, 24 * MHZ);
   473				_m = tmp;
   474				if (_m < 0x30 || _m > 0x7b)
   475					continue;
   476	
   477				/*
   478				 * Rev 2 of the Ref Manual states the
   479				 * VCO can range between 750MHz and
   480				 * 3GHz. The VCO is assumed to be
   481				 * Fvco = (M * f_ref) / P,
   482				 * where f_ref is 24MHz.
   483				 */
   484				tmp = (u64)_m * 24 * MHZ;
   485				do_div(tmp, _p);
   486				if (tmp < 750 * MHZ ||
   487				    tmp > 3000 * MHZ)
   488					continue;
   489	
   490				/* Final frequency after post-divider */
   491				do_div(tmp, _s);
   492	
   493				delta = abs(fout - tmp);
   494				if (delta < min_delta) {
   495					best_p = _p;
   496					best_s = _s;
   497					best_m = _m;
   498					min_delta = delta;
   499					best_freq = tmp;
   500				}
   501			}
   502		}
   503	
   504		if (best_freq) {
   505			*p = best_p;
   506			*m = best_m;
   507			*s = best_s;
   508		}
   509	
   510		return best_freq / 5;
   511	}
   512	

-- 
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