402 	u64 clocks;  in mpc52xx_gpt_do_start()  local
414 	/* Determine the number of clocks in the requested period.  64 bit  in mpc52xx_gpt_do_start()
418 	clocks = period * (u64)gpt->ipb_freq;  in mpc52xx_gpt_do_start()
419 	do_div(clocks, 1000000000); /* Scale it down to ns range */  in mpc52xx_gpt_do_start()
422 	if (clocks > 0xffffffff)  in mpc52xx_gpt_do_start()
425 	/* Calculate the prescaler and count values from the clocks value.  in mpc52xx_gpt_do_start()
426 	 * 'clocks' is the number of clock ticks in the period.  The timer  in mpc52xx_gpt_do_start()
428 	 * calculated by integer dividing the clocks by 0x10000 (shifting  in mpc52xx_gpt_do_start()
429 	 * down 16 bits) to obtain the smallest possible divisor for clocks  in mpc52xx_gpt_do_start()
437 	prescale = (clocks >> 16) + 1;  in mpc52xx_gpt_do_start()
438 	do_div(clocks, prescale);  in mpc52xx_gpt_do_start()
439 	if (clocks > 0xffff) {  in mpc52xx_gpt_do_start()
440 		pr_err("calculation error; prescale:%x clocks:%llx\n",  in mpc52xx_gpt_do_start()
441 		       prescale, clocks);  in mpc52xx_gpt_do_start()
453 	out_be32(&gpt->regs->count, prescale << 16 | clocks);  in mpc52xx_gpt_do_start()