Re: [PATCH 05/10] drm/bridge: Add Synopsys DesignWare MIPI DSI host controller driver

[kbuild test robot <lkp@intel.com>]

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Hi Chris,

[auto build test WARNING on rockchip/for-next -- if it's inappropriate base, please ignore]

config: i386-randconfig-h1-10111440 (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

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/bridge/dw_mipi_dsi.c: In function 'dw_mipi_dsi_bridge_mode_set':
   drivers/gpu/drm/bridge/dw_mipi_dsi.c:451:17: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
     dsi->input_div = n;
                    ^
   drivers/gpu/drm/bridge/dw_mipi_dsi.c:412:9: note: 'n' was declared here
     int m, n, pre;
            ^
   drivers/gpu/drm/bridge/dw_mipi_dsi.c:452:20: warning: 'm' may be used uninitialized in this function [-Wmaybe-uninitialized]
     dsi->feedback_div = m;
                       ^
   drivers/gpu/drm/bridge/dw_mipi_dsi.c:412:6: note: 'm' was declared here
     int m, n, pre;
         ^
   In file included from arch/x86/include/asm/realmode.h:5:0,
                    from arch/x86/include/asm/acpi.h:33,
                    from arch/x86/include/asm/fixmap.h:19,
                    from arch/x86/include/asm/apic.h:12,
                    from arch/x86/include/asm/smp.h:12,
                    from include/linux/smp.h:59,
                    from include/linux/topology.h:33,
                    from include/linux/gfp.h:8,
                    from include/linux/kmod.h:22,
                    from include/linux/module.h:13,
                    from drivers/gpu/drm/bridge/dw_mipi_dsi.c:12:
>> arch/x86/include/asm/io.h:53:3: warning: 'calor' may be used uninitialized in this function [-Wmaybe-uninitialized]
    { asm volatile("mov" size " %0,%1": :reg (val), \
      ^
   drivers/gpu/drm/bridge/dw_mipi_dsi.c:763:15: note: 'calor' was declared here
     u32 val = 0, calor;
                  ^
   drivers/gpu/drm/bridge/dw_mipi_dsi.c:410:15: warning: 'max_mbps' may be used uninitialized in this function [-Wmaybe-uninitialized]
     unsigned int max_mbps, target_mbps = 1000;
                  ^

vim +/calor +53 arch/x86/include/asm/io.h

b310f381d include/asm-x86/io.h      venkatesh.pallipadi@intel.com 2008-03-18  37  #define ARCH_HAS_IOREMAP_WC
d838270e2 arch/x86/include/asm/io.h Toshi Kani                    2015-06-04  38  #define ARCH_HAS_IOREMAP_WT
b310f381d include/asm-x86/io.h      venkatesh.pallipadi@intel.com 2008-03-18  39  
1c5b9069e arch/x86/include/asm/io.h Brian Gerst                   2010-02-05  40  #include <linux/string.h>
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  41  #include <linux/compiler.h>
976e8f677 arch/x86/include/asm/io.h Jeremy Fitzhardinge           2009-02-06  42  #include <asm/page.h>
5b7c73e00 arch/x86/include/asm/io.h Mark Salter                   2014-04-07  43  #include <asm/early_ioremap.h>
d6472302f arch/x86/include/asm/io.h Stephen Rothwell              2015-06-02  44  #include <asm/pgtable_types.h>
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  45  
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  46  #define build_mmio_read(name, size, type, reg, barrier) \
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  47  static inline type name(const volatile void __iomem *addr) \
1c5b0eb66 include/asm-x86/io.h      Mikael Pettersson             2008-08-13  48  { type ret; asm volatile("mov" size " %1,%0":reg (ret) \
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  49  :"m" (*(volatile type __force *)addr) barrier); return ret; }
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  50  
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  51  #define build_mmio_write(name, size, type, reg, barrier) \
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  52  static inline void name(type val, volatile void __iomem *addr) \
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27 @53  { asm volatile("mov" size " %0,%1": :reg (val), \
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  54  "m" (*(volatile type __force *)addr) barrier); }
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  55  
1c5b0eb66 include/asm-x86/io.h      Mikael Pettersson             2008-08-13  56  build_mmio_read(readb, "b", unsigned char, "=q", :"memory")
1c5b0eb66 include/asm-x86/io.h      Mikael Pettersson             2008-08-13  57  build_mmio_read(readw, "w", unsigned short, "=r", :"memory")
1c5b0eb66 include/asm-x86/io.h      Mikael Pettersson             2008-08-13  58  build_mmio_read(readl, "l", unsigned int, "=r", :"memory")
c1f64a580 include/asm-x86/io.h      Linus Torvalds                2008-05-27  59  
1c5b0eb66 include/asm-x86/io.h      Mikael Pettersson             2008-08-13  60  build_mmio_read(__readb, "b", unsigned char, "=q", )
1c5b0eb66 include/asm-x86/io.h      Mikael Pettersson             2008-08-13  61  build_mmio_read(__readw, "w", unsigned short, "=r", )

:::::: The code at line 53 was first introduced by commit
:::::: c1f64a58003fd2efaa725a857e269a15f765791a x86: MMIO and gcc re-ordering issue

:::::: TO: Linus Torvalds <torvalds@linux-foundation.org>
:::::: CC: Ingo Molnar <mingo@elte.hu>

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