[PATCH v2 02/10] drm/tilcdc: Allow build with COMPILE_TEST=y

[kernel test robot]

Hi Ville,

kernel test robot noticed the following build warnings:

[auto build test WARNING on next-20241003]
[cannot apply to shawnguo/for-next linus/master rmk-arm/drm-armada-devel rmk-arm/drm-armada-fixes v6.12-rc1 v6.11 v6.11-rc7 v6.12-rc1]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ville-Syrjala/drm-tilcdc-Allow-build-without-__iowmb/20241003-192043
base:   next-20241003
patch link:    https://lore.kernel.org/r/20241003111851.10453-3-ville.syrjala%40linux.intel.com
patch subject: [PATCH v2 02/10] drm/tilcdc: Allow build with COMPILE_TEST=y
config: alpha-allyesconfig (https://download.01.org/0day-ci/archive/20241004/202410042345.cQDnF4wd-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 13.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241004/202410042345.cQDnF4wd-lkp@intel.com/reproduce)

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 at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410042345.cQDnF4wd-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/gpu/drm/tilcdc/tilcdc_crtc.c:24:
   drivers/gpu/drm/tilcdc/tilcdc_regs.h: In function 'tilcdc_write64':
>> drivers/gpu/drm/tilcdc/tilcdc_regs.h:126:25: warning: passing argument 2 of 'iowrite64' discards 'volatile' qualifier from pointer target type [-Wdiscarded-qualifiers]
     126 |         iowrite64(data, addr);
         |                         ^~~~
   In file included from arch/alpha/include/asm/io.h:15,
                    from include/linux/scatterlist.h:9,
                    from include/linux/dma-mapping.h:11,
                    from drivers/gpu/drm/tilcdc/tilcdc_crtc.c:8:
   include/asm-generic/iomap.h:56:28: note: expected 'void *' but argument is of type 'volatile void *'
      56 | extern void iowrite64(u64, void __iomem *);
         |                            ^~~~~~~~~~~~~~


vim +126 drivers/gpu/drm/tilcdc/tilcdc_regs.h

16ea975eac671f Rob Clark       2013-01-08  119  
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  120  static inline void tilcdc_write64(struct drm_device *dev, u32 reg, u64 data)
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  121  {
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  122  	struct tilcdc_drm_private *priv = dev->dev_private;
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  123  	volatile void __iomem *addr = priv->mmio + reg;
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  124  
4e5ca2d930aa87 Logan Gunthorpe 2017-12-05  125  #if defined(iowrite64) && !defined(iowrite64_is_nonatomic)
7eb9f069ff5dd3 Jyri Sarha      2016-08-26 @126  	iowrite64(data, addr);
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  127  #else
d5b0aa96231c76 Ville Syrjälä   2024-10-03  128  	/* allow compilation without __iowmb() for COMPILE_TEST */
d5b0aa96231c76 Ville Syrjälä   2024-10-03  129  #ifdef __iowmb
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  130  	__iowmb();
d5b0aa96231c76 Ville Syrjälä   2024-10-03  131  #endif
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  132  	/* This compiles to strd (=64-bit write) on ARM7 */
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  133  	*(volatile u64 __force *)addr = __cpu_to_le64(data);
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  134  #endif
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  135  }
7eb9f069ff5dd3 Jyri Sarha      2016-08-26  136  

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