linux-kernel - [kbuild] [drm-drm-misc:drm-misc-next 10/24] drivers/gpu/drm/mgag200/mgag200_pll.c:142 mgag200_pixpll_compute_g200se_00() error: uninitialized symbol 'delta'.

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Message-ID: <202108121820.0bO8dsT7-lkp@intel.com>
Date:   Thu, 12 Aug 2021 14:51:09 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Thomas Zimmermann <tzimmermann@...e.de>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: [kbuild] [drm-drm-misc:drm-misc-next 10/24]
 drivers/gpu/drm/mgag200/mgag200_pll.c:142 mgag200_pixpll_compute_g200se_00()
 error: uninitialized symbol 'delta'.

tree:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
head:   2ca380ea0e6a31046b7c4048e3f61cfc2f6b2aa3
commit: 2545ac960364d0395802a27374b46f13827b4cf5 [10/24] drm/mgag200: Abstract pixel PLL via struct mgag200_pll
config: x86_64-randconfig-m001-20210812 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

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

smatch warnings:
drivers/gpu/drm/mgag200/mgag200_pll.c:142 mgag200_pixpll_compute_g200se_00() error: uninitialized symbol 'delta'.

vim +/delta +142 drivers/gpu/drm/mgag200/mgag200_pll.c

2545ac960364d0 Thomas Zimmermann 2021-07-14  114  static int mgag200_pixpll_compute_g200se_00(struct mgag200_pll *pixpll, long clock,
2545ac960364d0 Thomas Zimmermann 2021-07-14  115  					    struct mgag200_pll_values *pixpllc)
2545ac960364d0 Thomas Zimmermann 2021-07-14  116  {
2545ac960364d0 Thomas Zimmermann 2021-07-14  117  	static const unsigned int vcomax = 320000;
2545ac960364d0 Thomas Zimmermann 2021-07-14  118  	static const unsigned int vcomin = 160000;
2545ac960364d0 Thomas Zimmermann 2021-07-14  119  	static const unsigned int pllreffreq = 25000;
2545ac960364d0 Thomas Zimmermann 2021-07-14  120  
2545ac960364d0 Thomas Zimmermann 2021-07-14  121  	unsigned int delta, tmpdelta, permitteddelta;
                                                        ^^^^^^^^^^^^^^^^^^
2545ac960364d0 Thomas Zimmermann 2021-07-14  122  	unsigned int testp, testm, testn;
2545ac960364d0 Thomas Zimmermann 2021-07-14  123  	unsigned int p, m, n, s;
2545ac960364d0 Thomas Zimmermann 2021-07-14  124  	unsigned int computed;
2545ac960364d0 Thomas Zimmermann 2021-07-14  125  
2545ac960364d0 Thomas Zimmermann 2021-07-14  126  	m = n = p = s = 0;
2545ac960364d0 Thomas Zimmermann 2021-07-14  127  	permitteddelta = clock * 5 / 1000;
2545ac960364d0 Thomas Zimmermann 2021-07-14  128  
2545ac960364d0 Thomas Zimmermann 2021-07-14  129  	for (testp = 8; testp > 0; testp /= 2) {
2545ac960364d0 Thomas Zimmermann 2021-07-14  130  		if (clock * testp > vcomax)
2545ac960364d0 Thomas Zimmermann 2021-07-14  131  			continue;
2545ac960364d0 Thomas Zimmermann 2021-07-14  132  		if (clock * testp < vcomin)
2545ac960364d0 Thomas Zimmermann 2021-07-14  133  			continue;
2545ac960364d0 Thomas Zimmermann 2021-07-14  134  
2545ac960364d0 Thomas Zimmermann 2021-07-14  135  		for (testn = 17; testn < 256; testn++) {
2545ac960364d0 Thomas Zimmermann 2021-07-14  136  			for (testm = 1; testm < 32; testm++) {
2545ac960364d0 Thomas Zimmermann 2021-07-14  137  				computed = (pllreffreq * testn) / (testm * testp);
2545ac960364d0 Thomas Zimmermann 2021-07-14  138  				if (computed > clock)
2545ac960364d0 Thomas Zimmermann 2021-07-14  139  					tmpdelta = computed - clock;
2545ac960364d0 Thomas Zimmermann 2021-07-14  140  				else
2545ac960364d0 Thomas Zimmermann 2021-07-14  141  					tmpdelta = clock - computed;
2545ac960364d0 Thomas Zimmermann 2021-07-14 @142  				if (tmpdelta < delta) {

"delta" is not intialized until the next line.


2545ac960364d0 Thomas Zimmermann 2021-07-14  143  					delta = tmpdelta;
2545ac960364d0 Thomas Zimmermann 2021-07-14  144  					m = testm;
2545ac960364d0 Thomas Zimmermann 2021-07-14  145  					n = testn;
2545ac960364d0 Thomas Zimmermann 2021-07-14  146  					p = testp;
2545ac960364d0 Thomas Zimmermann 2021-07-14  147  				}
2545ac960364d0 Thomas Zimmermann 2021-07-14  148  			}
2545ac960364d0 Thomas Zimmermann 2021-07-14  149  		}
2545ac960364d0 Thomas Zimmermann 2021-07-14  150  	}
2545ac960364d0 Thomas Zimmermann 2021-07-14  151  
2545ac960364d0 Thomas Zimmermann 2021-07-14  152  	if (delta > permitteddelta) {
2545ac960364d0 Thomas Zimmermann 2021-07-14  153  		pr_warn("PLL delta too large\n");
2545ac960364d0 Thomas Zimmermann 2021-07-14  154  		return -EINVAL;
2545ac960364d0 Thomas Zimmermann 2021-07-14  155  	}
2545ac960364d0 Thomas Zimmermann 2021-07-14  156  
2545ac960364d0 Thomas Zimmermann 2021-07-14  157  	pixpllc->m = m;
2545ac960364d0 Thomas Zimmermann 2021-07-14  158  	pixpllc->n = n;
2545ac960364d0 Thomas Zimmermann 2021-07-14  159  	pixpllc->p = p;
2545ac960364d0 Thomas Zimmermann 2021-07-14  160  	pixpllc->s = s;
2545ac960364d0 Thomas Zimmermann 2021-07-14  161  
2545ac960364d0 Thomas Zimmermann 2021-07-14  162  	return 0;
2545ac960364d0 Thomas Zimmermann 2021-07-14  163  }

---
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