// SPDX-License-Identifier: GPL-2.0

  #include <linux/bug.h>

  #include <linux/kernel.h>

  #include <asm/div64.h>
  #include <linux/reciprocal_div.h>

  #include <linux/export.h>

  /*
   * For a description of the algorithm please have a look at
   * include/linux/reciprocal_div.h
   */
  
  struct reciprocal_value reciprocal_value(u32 d)

  {

  	struct reciprocal_value R;
  	u64 m;
  	int l;
  
  	l = fls(d - 1);
  	m = ((1ULL << 32) * ((1ULL << l) - d));
  	do_div(m, d);
  	++m;
  	R.m = (u32)m;
  	R.sh1 = min(l, 1);
  	R.sh2 = max(l - 1, 0);
  
  	return R;

  }

  EXPORT_SYMBOL(reciprocal_value);

  
  struct reciprocal_value_adv reciprocal_value_adv(u32 d, u8 prec)
  {
  	struct reciprocal_value_adv R;
  	u32 l, post_shift;
  	u64 mhigh, mlow;
  
  	/* ceil(log2(d)) */
  	l = fls(d - 1);
  	/* NOTE: mlow/mhigh could overflow u64 when l == 32. This case needs to
  	 * be handled before calling "reciprocal_value_adv", please see the
  	 * comment at include/linux/reciprocal_div.h.
  	 */
  	WARN(l == 32,
  	     "ceil(log2(0x%08x)) == 32, %s doesn't support such divisor",
  	     d, __func__);
  	post_shift = l;
  	mlow = 1ULL << (32 + l);
  	do_div(mlow, d);
  	mhigh = (1ULL << (32 + l)) + (1ULL << (32 + l - prec));
  	do_div(mhigh, d);
  
  	for (; post_shift > 0; post_shift--) {
  		u64 lo = mlow >> 1, hi = mhigh >> 1;
  
  		if (lo >= hi)
  			break;
  
  		mlow = lo;
  		mhigh = hi;
  	}
  
  	R.m = (u32)mhigh;
  	R.sh = post_shift;
  	R.exp = l;
  	R.is_wide_m = mhigh > U32_MAX;
  
  	return R;
  }
  EXPORT_SYMBOL(reciprocal_value_adv);