[Intel-gfx] [PATCH 08/29] drm/dp: Add helpers to calculate the link BW overhead

[kernel test robot]

Hi Imre,

kernel test robot noticed the following build errors:

[auto build test ERROR on drm-tip/drm-tip]

url:    https://github.com/intel-lab-lkp/linux/commits/Imre-Deak/drm-dp_mst-Fix-fractional-DSC-bpp-handling/20231024-091920
base:   git://anongit.freedesktop.org/drm/drm-tip drm-tip
patch link:    https://lore.kernel.org/r/20231024010925.3949910-9-imre.deak%40intel.com
patch subject: [Intel-gfx] [PATCH 08/29] drm/dp: Add helpers to calculate the link BW overhead
config: arm-s5pv210_defconfig (https://download.01.org/0day-ci/archive/20231025/202310252345.i0qKzGuh-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231025/202310252345.i0qKzGuh-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/202310252345.i0qKzGuh-lkp@intel.com/

All errors (new ones prefixed by >>):

   arm-linux-gnueabi-ld: drivers/gpu/drm/display/drm_dp_mst_topology.o: in function `drm_dp_calc_pbn_mode':
>> drivers/gpu/drm/display/drm_dp_mst_topology.c:4745:(.text+0x12b0): undefined reference to `drm_dp_bw_overhead'


vim +4745 drivers/gpu/drm/display/drm_dp_mst_topology.c

  4718	
  4719	/**
  4720	 * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
  4721	 * @clock: dot clock
  4722	 * @bpp: bpp as .4 binary fixed point
  4723	 *
  4724	 * This uses the formula in the spec to calculate the PBN value for a mode.
  4725	 */
  4726	int drm_dp_calc_pbn_mode(int clock, int bpp)
  4727	{
  4728		/*
  4729		 * The unit of 54/64Mbytes/sec is an arbitrary unit chosen based on
  4730		 * common multiplier to render an integer PBN for all link rate/lane
  4731		 * counts combinations
  4732		 * calculate
  4733		 * peak_kbps = clock * bpp / 16
  4734		 * peak_kbps *= SSC overhead / 1000000
  4735		 * peak_kbps /= 8    convert to Kbytes
  4736		 * peak_kBps *= (64/54) / 1000    convert to PBN
  4737		 */
  4738		/*
  4739		 * TODO: Use the actual link and mode parameters to calculate
  4740		 * the overhead. For now it's assumed that these are
  4741		 * 4 link lanes, 4096 hactive pixels, which don't add any
  4742		 * significant data padding overhead and that there is no DSC
  4743		 * or FEC overhead.
  4744		 */
> 4745		int overhead = drm_dp_bw_overhead(4, 4096, 0, bpp,
  4746						  DRM_DP_BW_OVERHEAD_MST |
  4747						  DRM_DP_BW_OVERHEAD_SSC);
  4748	
  4749		return DIV64_U64_ROUND_UP(mul_u32_u32(clock * bpp, 64 * overhead >> 4),
  4750					  1000000ULL * 8 * 54 * 1000);
  4751	}
  4752	EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
  4753	

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