u-boot/board/hidden_dragon/speed.h

/*
 * (C) Copyright 2000
 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

/*-----------------------------------------------------------------------
 * Timer value for timer 2, ICLK = 10
 *
 * SPEED_FCOUNT2 =  GCLK / (16 * (TIMER_TMR_PS + 1))
 * SPEED_TMR3_PS = (GCLK / (16 * SPEED_FCOUNT3)) - 1
 *
 * SPEED_FCOUNT2	timer 2 counting frequency
 * GCLK			CPU clock
 * SPEED_TMR2_PS	prescaler
 */
#define SPEED_TMR2_PS	(250 - 1)	/* divide by 250	*/

/*-----------------------------------------------------------------------
 * Timer value for PIT
 *
 * PIT_TIME = SPEED_PITC / PITRTCLK
 * PITRTCLK = 8192
 */
#define SPEED_PITC	(82 << 16)	/* start counting from 82	*/

/*
 * The new value for PTA is calculated from
 *
 *	PTA = (gclk * Trefresh) / (2 ^ (2 * DFBRG) * PTP * NCS)
 *
 * gclk		CPU clock (not bus clock !)
 * Trefresh	Refresh cycle * 4 (four word bursts used)
 * DFBRG	For normal mode (no clock reduction) always 0
 * PTP		Prescaler (already adjusted for no. of banks and 4K / 8K refresh)
 * NCS		Number of SDRAM banks (chip selects) on this UPM.
 */