Hi,

[auto build test WARNING on drm-intel/for-linux-next]
[also build test WARNING on next-20160420]
[cannot apply to v4.6-rc4]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improving the system]

url:    
https://github.com/0day-ci/linux/commits/Matt-Roper/Pre-calculate-SKL-style-atomic-watermarks/20160420-102913
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
config: x86_64-randconfig-n0-04210735 (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers/gpu/drm/i915/intel_pm.c: In function 'skl_compute_wm':
>> drivers/gpu/drm/i915/intel_pm.c:2903:5: warning: 'num_active' may be used 
>> uninitialized in this function [-Wmaybe-uninitialized]
     if (num_active == 1)
        ^
   drivers/gpu/drm/i915/intel_pm.c:3057:6: note: 'num_active' was declared here
     int num_active;
         ^

vim +/num_active +2903 drivers/gpu/drm/i915/intel_pm.c

000bcc21 Matt Roper     2016-04-19  2887        if 
(!intel_state->active_pipe_changes) {
000bcc21 Matt Roper     2016-04-19  2888                *alloc = 
dev_priv->wm.skl_hw.ddb.pipe[pipe];
000bcc21 Matt Roper     2016-04-19  2889                *num_active = 
hweight32(dev_priv->active_crtcs);
000bcc21 Matt Roper     2016-04-19  2890                return;
000bcc21 Matt Roper     2016-04-19  2891        }
000bcc21 Matt Roper     2016-04-19  2892  
000bcc21 Matt Roper     2016-04-19  2893        *num_active = 
hweight32(intel_state->active_crtcs);
000bcc21 Matt Roper     2016-04-19  2894        nth_active_pipe = 
hweight32(intel_state->active_crtcs &
000bcc21 Matt Roper     2016-04-19  2895                                    
(drm_crtc_mask(for_crtc) - 1));
000bcc21 Matt Roper     2016-04-19  2896        pipe_size = ddb_size / 
hweight32(intel_state->active_crtcs);
000bcc21 Matt Roper     2016-04-19  2897        alloc->start = nth_active_pipe 
* ddb_size / *num_active;
000bcc21 Matt Roper     2016-04-19  2898        alloc->end = alloc->start + 
pipe_size;
b9cec075 Damien Lespiau 2014-11-04  2899  }
b9cec075 Damien Lespiau 2014-11-04  2900  
000bcc21 Matt Roper     2016-04-19  2901  static unsigned int 
skl_cursor_allocation(int num_active)
b9cec075 Damien Lespiau 2014-11-04  2902  {
000bcc21 Matt Roper     2016-04-19 @2903        if (num_active == 1)
b9cec075 Damien Lespiau 2014-11-04  2904                return 32;
b9cec075 Damien Lespiau 2014-11-04  2905  
b9cec075 Damien Lespiau 2014-11-04  2906        return 8;
b9cec075 Damien Lespiau 2014-11-04  2907  }
b9cec075 Damien Lespiau 2014-11-04  2908  
a269c583 Damien Lespiau 2014-11-04  2909  static void 
skl_ddb_entry_init_from_hw(struct skl_ddb_entry *entry, u32 reg)
a269c583 Damien Lespiau 2014-11-04  2910  {
a269c583 Damien Lespiau 2014-11-04  2911        entry->start = reg & 0x3ff;

:::::: The code at line 2903 was first introduced by commit
:::::: 000bcc2112fef02e609ad72f6ae43fd027ce8564 drm/i915/gen9: Allow 
skl_allocate_pipe_ddb() to operate on in-flight state (v2)

:::::: TO: Matt Roper <[email protected]>
:::::: CC: 0day robot <[email protected]>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Attachment: .config.gz
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