arch/powerpc/cpu/ppc4xx/40x_spd_sdram.c - uboot/armada - Git at Google

 /*
  * arch/powerpc/cpu/ppc4xx/40x_spd_sdram.c
  * This SPD SDRAM detection code supports IBM/AMCC PPC44x cpu with a
  * SDRAM controller. Those are all current 405 PPC's.
  *
  * (C) Copyright 2001
  * Bill Hunter, Wave 7 Optics, williamhunter@attbi.com
  *
  * Based on code by:
  *
  * Kenneth Johansson ,Ericsson AB.
  * kenneth.johansson@etx.ericsson.se
  *
  * hacked up by bill hunter. fixed so we could run before
  * serial_init and console_init. previous version avoided this by
  * running out of cache memory during serial/console init, then running
  * this code later.
  *
  * (C) Copyright 2002
  * Jun Gu, Artesyn Technology, jung@artesyncp.com
  * Support for AMCC 440 based on OpenBIOS draminit.c from IBM.
  *
  * (C) Copyright 2005
  * Stefan Roese, DENX Software Engineering, sr@denx.de.
  *
  * See file CREDITS for list of people who contributed to this
  * project.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation; either version 2 of
  * the License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  * MA 02111-1307 USA
  */

 #include <common.h>
 #include <asm/processor.h>
 #include <i2c.h>
 #include <asm/ppc4xx.h>

 #if defined(CONFIG_SPD_EEPROM) && !defined(CONFIG_440)

 /*
  * Set default values
  */
 #ifndef CONFIG_SYS_I2C_SPEED
 #define CONFIG_SYS_I2C_SPEED	50000
 #endif

 #define ONE_BILLION	1000000000

 #define	 SDRAM0_CFG_DCE		0x80000000
 #define	 SDRAM0_CFG_SRE		0x40000000
 #define	 SDRAM0_CFG_PME		0x20000000
 #define	 SDRAM0_CFG_MEMCHK	0x10000000
 #define	 SDRAM0_CFG_REGEN	0x08000000
 #define	 SDRAM0_CFG_ECCDD	0x00400000
 #define	 SDRAM0_CFG_EMDULR	0x00200000
 #define	 SDRAM0_CFG_DRW_SHIFT	(31-6)
 #define	 SDRAM0_CFG_BRPF_SHIFT	(31-8)

 #define	 SDRAM0_TR_CASL_SHIFT	(31-8)
 #define	 SDRAM0_TR_PTA_SHIFT	(31-13)
 #define	 SDRAM0_TR_CTP_SHIFT	(31-15)
 #define	 SDRAM0_TR_LDF_SHIFT	(31-17)
 #define	 SDRAM0_TR_RFTA_SHIFT	(31-29)
 #define	 SDRAM0_TR_RCD_SHIFT	(31-31)

 #define	 SDRAM0_RTR_SHIFT	(31-15)
 #define	 SDRAM0_ECCCFG_SHIFT	(31-11)

 /* SDRAM0_CFG enable macro  */
 #define SDRAM0_CFG_BRPF(x) ( ( x & 0x3)<< SDRAM0_CFG_BRPF_SHIFT )

 #define SDRAM0_BXCR_SZ_MASK	0x000e0000
 #define SDRAM0_BXCR_AM_MASK	0x0000e000

 #define SDRAM0_BXCR_SZ_SHIFT	(31-14)
 #define SDRAM0_BXCR_AM_SHIFT	(31-18)

 #define SDRAM0_BXCR_SZ(x)	( (( x << SDRAM0_BXCR_SZ_SHIFT) & SDRAM0_BXCR_SZ_MASK) )
 #define SDRAM0_BXCR_AM(x)	( (( x << SDRAM0_BXCR_AM_SHIFT) & SDRAM0_BXCR_AM_MASK) )

 #ifdef CONFIG_SPDDRAM_SILENT
 # define SPD_ERR(x) do { return 0; } while (0)
 #else
 # define SPD_ERR(x) do { printf(x); return(0); } while (0)
 #endif

 #define sdram_HZ_to_ns(hertz) (1000000000/(hertz))

 /* function prototypes */
 int spd_read(uint addr);


 /*
  * This function is reading data from the DIMM module EEPROM over the SPD bus
  * and uses that to program the sdram controller.
  *
  * This works on boards that has the same schematics that the AMCC walnut has.
  *
  * Input: null for default I2C spd functions or a pointer to a custom function
  * returning spd_data.
  */

 long int spd_sdram(int(read_spd)(uint addr))
 {
 	int tmp,row,col;
 	int total_size,bank_size,bank_code;
 	int mode;
 	int bank_cnt;

 	int sdram0_pmit=0x07c00000;
 	int sdram0_b0cr;
 	int sdram0_b1cr = 0;
 #ifndef CONFIG_405EP /* not on PPC405EP */
 	int sdram0_b2cr = 0;
 	int sdram0_b3cr = 0;
 	int sdram0_besr0 = -1;
 	int sdram0_besr1 = -1;
 	int sdram0_eccesr = -1;
 	int sdram0_ecccfg;
 	int ecc_on;
 #endif

 	int sdram0_rtr=0;
 	int sdram0_tr=0;

 	int sdram0_cfg=0;

 	int t_rp;
 	int t_rcd;
 	int t_ras;
 	int t_rc;
 	int min_cas;

 	PPC4xx_SYS_INFO sys_info;
 	unsigned long bus_period_x_10;

 	/*
 	 * get the board info
 	 */
 	get_sys_info(&sys_info);
 	bus_period_x_10 = ONE_BILLION / (sys_info.freqPLB / 10);

 	if (read_spd == 0){
 		read_spd=spd_read;
 		/*
 		 * Make sure I2C controller is initialized
 		 * before continuing.
 		 */
 		i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
 	}

 	/* Make shure we are using SDRAM */
 	if (read_spd(2) != 0x04) {
 		SPD_ERR("SDRAM - non SDRAM memory module found\n");
 	}

 	/* ------------------------------------------------------------------
 	 * configure memory timing register
 	 *
 	 * data from DIMM:
 	 * 27	IN Row Precharge Time ( t RP)
 	 * 29	MIN RAS to CAS Delay ( t RCD)
 	 * 127	 Component and Clock Detail ,clk0-clk3, junction temp, CAS
 	 * -------------------------------------------------------------------*/

 	/*
 	 * first figure out which cas latency mode to use
 	 * use the min supported mode
 	 */

 	tmp = read_spd(127) & 0x6;
 	if (tmp == 0x02) {		/* only cas = 2 supported */
 		min_cas = 2;
 /*		t_ck = read_spd(9); */
 /*		t_ac = read_spd(10); */
 	} else if (tmp == 0x04) {	/* only cas = 3 supported */
 		min_cas = 3;
 /*		t_ck = read_spd(9); */
 /*		t_ac = read_spd(10); */
 	} else if (tmp == 0x06) {	/* 2,3 supported, so use 2 */
 		min_cas = 2;
 /*		t_ck = read_spd(23); */
 /*		t_ac = read_spd(24); */
 	} else {
 		SPD_ERR("SDRAM - unsupported CAS latency \n");
 	}

 	/* get some timing values, t_rp,t_rcd,t_ras,t_rc
 	 */
 	t_rp = read_spd(27);
 	t_rcd = read_spd(29);
 	t_ras = read_spd(30);
 	t_rc = t_ras + t_rp;

 	/* The following timing calcs subtract 1 before deviding.
 	 * this has effect of using ceiling instead of floor rounding,
 	 * and also subtracting 1 to convert number to reg value
 	 */
 	/* set up CASL */
 	sdram0_tr = (min_cas - 1) << SDRAM0_TR_CASL_SHIFT;
 	/* set up PTA */
 	sdram0_tr |= ((((t_rp - 1) * 10)/bus_period_x_10) & 0x3) << SDRAM0_TR_PTA_SHIFT;
 	/* set up CTP */
 	tmp = (((t_rc - t_rcd - t_rp -1) * 10) / bus_period_x_10) & 0x3;
 	if (tmp < 1)
 		tmp = 1;
 	sdram0_tr |= tmp << SDRAM0_TR_CTP_SHIFT;
 	/* set LDF	= 2 cycles, reg value = 1 */
 	sdram0_tr |= 1 << SDRAM0_TR_LDF_SHIFT;
 	/* set RFTA = t_rfc/bus_period, use t_rfc = t_rc */
 	tmp = (((t_rc - 1) * 10) / bus_period_x_10) - 3;
 	if (tmp < 0)
 		tmp = 0;
 	if (tmp > 6)
 		tmp = 6;
 	sdram0_tr |= tmp << SDRAM0_TR_RFTA_SHIFT;
 	/* set RCD = t_rcd/bus_period*/
 	sdram0_tr |= ((((t_rcd - 1) * 10) / bus_period_x_10) &0x3) << SDRAM0_TR_RCD_SHIFT ;


 	/*------------------------------------------------------------------
 	 * configure RTR register
 	 * -------------------------------------------------------------------*/
 	row = read_spd(3);
 	col = read_spd(4);
 	tmp = read_spd(12) & 0x7f ; /* refresh type less self refresh bit */
 	switch (tmp) {
 	case 0x00:
 		tmp = 15625;
 		break;
 	case 0x01:
 		tmp = 15625 / 4;
 		break;
 	case 0x02:
 		tmp = 15625 / 2;
 		break;
 	case 0x03:
 		tmp = 15625 * 2;
 		break;
 	case 0x04:
 		tmp = 15625 * 4;
 		break;
 	case 0x05:
 		tmp = 15625 * 8;
 		break;
 	default:
 		SPD_ERR("SDRAM - Bad refresh period \n");
 	}
 	/* convert from nsec to bus cycles */
 	tmp = (tmp * 10) / bus_period_x_10;
 	sdram0_rtr = (tmp & 0x3ff8) <<	SDRAM0_RTR_SHIFT;

 	/*------------------------------------------------------------------
 	 * determine the number of banks used
 	 * -------------------------------------------------------------------*/
 	/* byte 7:6 is module data width */
 	if (read_spd(7) != 0)
 		SPD_ERR("SDRAM - unsupported module width\n");
 	tmp = read_spd(6);
 	if (tmp < 32)
 		SPD_ERR("SDRAM - unsupported module width\n");
 	else if (tmp < 64)
 		bank_cnt = 1;		/* one bank per sdram side */
 	else if (tmp < 73)
 		bank_cnt = 2;	/* need two banks per side */
 	else if (tmp < 161)
 		bank_cnt = 4;	/* need four banks per side */
 	else
 		SPD_ERR("SDRAM - unsupported module width\n");

 	/* byte 5 is the module row count (refered to as dimm "sides") */
 	tmp = read_spd(5);
 	if (tmp == 1)
 		;
 	else if (tmp==2)
 		bank_cnt *= 2;
 	else if (tmp==4)
 		bank_cnt *= 4;
 	else
 		bank_cnt = 8;		/* 8 is an error code */

 	if (bank_cnt > 4)	/* we only have 4 banks to work with */
 		SPD_ERR("SDRAM - unsupported module rows for this width\n");

 #ifndef CONFIG_405EP /* not on PPC405EP */
 	/* now check for ECC ability of module. We only support ECC
 	 *   on 32 bit wide devices with 8 bit ECC.
 	 */
 	if ((read_spd(11)==2) && (read_spd(6)==40) && (read_spd(14)==8)) {
 		sdram0_ecccfg = 0xf << SDRAM0_ECCCFG_SHIFT;
 		ecc_on = 1;
 	} else {
 		sdram0_ecccfg = 0;
 		ecc_on = 0;
 	}
 #endif

 	/*------------------------------------------------------------------
 	 * calculate total size
 	 * -------------------------------------------------------------------*/
 	/* calculate total size and do sanity check */
 	tmp = read_spd(31);
 	total_size = 1 << 22;	/* total_size = 4MB */
 	/* now multiply 4M by the smallest device row density */
 	/* note that we don't support asymetric rows */
 	while (((tmp & 0x0001) == 0) && (tmp != 0)) {
 		total_size = total_size << 1;
 		tmp = tmp >> 1;
 	}
 	total_size *= read_spd(5);	/* mult by module rows (dimm sides) */

 	/*------------------------------------------------------------------
 	 * map	rows * cols * banks to a mode
 	 * -------------------------------------------------------------------*/

 	switch (row) {
 	case 11:
 		switch (col) {
 		case 8:
 			mode=4; /* mode 5 */
 			break;
 		case 9:
 		case 10:
 			mode=0; /* mode 1 */
 			break;
 		default:
 			SPD_ERR("SDRAM - unsupported mode\n");
 		}
 		break;
 	case 12:
 		switch (col) {
 		case 8:
 			mode=3; /* mode 4 */
 			break;
 		case 9:
 		case 10:
 			mode=1; /* mode 2 */
 			break;
 		default:
 			SPD_ERR("SDRAM - unsupported mode\n");
 		}
 		break;
 	case 13:
 		switch (col) {
 		case 8:
 			mode=5; /* mode 6 */
 			break;
 		case 9:
 		case 10:
 			if (read_spd(17) == 2)
 				mode = 6; /* mode 7 */
 			else
 				mode = 2; /* mode 3 */
 			break;
 		case 11:
 			mode = 2; /* mode 3 */
 			break;
 		default:
 			SPD_ERR("SDRAM - unsupported mode\n");
 		}
 		break;
 	default:
 		SPD_ERR("SDRAM - unsupported mode\n");
 	}

 	/*------------------------------------------------------------------
 	 * using the calculated values, compute the bank
 	 * config register values.
 	 * -------------------------------------------------------------------*/

 	/* compute the size of each bank */
 	bank_size = total_size / bank_cnt;
 	/* convert bank size to bank size code for ppc4xx
 	   by takeing log2(bank_size) - 22 */
 	tmp = bank_size;		/* start with tmp = bank_size */
 	bank_code = 0;			/* and bank_code = 0 */
 	while (tmp > 1) {		/* this takes log2 of tmp */
 		bank_code++;		/* and stores result in bank_code */
 		tmp = tmp >> 1;
 	}				/* bank_code is now log2(bank_size) */
 	bank_code -= 22;		/* subtract 22 to get the code */

 	tmp = SDRAM0_BXCR_SZ(bank_code) | SDRAM0_BXCR_AM(mode) | 1;
 	sdram0_b0cr = (bank_size * 0) | tmp;
 #ifndef CONFIG_405EP /* not on PPC405EP */
 	if (bank_cnt > 1)
 		sdram0_b2cr = (bank_size * 1) | tmp;
 	if (bank_cnt > 2)
 		sdram0_b1cr = (bank_size * 2) | tmp;
 	if (bank_cnt > 3)
 		sdram0_b3cr = (bank_size * 3) | tmp;
 #else
 	/* PPC405EP chip only supports two SDRAM banks */
 	if (bank_cnt > 1)
 		sdram0_b1cr = (bank_size * 1) | tmp;
 	if (bank_cnt > 2)
 		total_size = 2 * bank_size;
 #endif

 	/*
 	 *   enable sdram controller DCE=1
 	 *  enable burst read prefetch to 32 bytes BRPF=2
 	 *  leave other functions off
 	 */

 	/*------------------------------------------------------------------
 	 * now that we've done our calculations, we are ready to
 	 * program all the registers.
 	 * -------------------------------------------------------------------*/

 	/* disable memcontroller so updates work */
 	mtsdram(SDRAM0_CFG, 0);

 #ifndef CONFIG_405EP /* not on PPC405EP */
 	mtsdram(SDRAM0_BESR0, sdram0_besr0);
 	mtsdram(SDRAM0_BESR1, sdram0_besr1);
 	mtsdram(SDRAM0_ECCCFG, sdram0_ecccfg);
 	mtsdram(SDRAM0_ECCESR, sdram0_eccesr);
 #endif
 	mtsdram(SDRAM0_RTR, sdram0_rtr);
 	mtsdram(SDRAM0_PMIT, sdram0_pmit);
 	mtsdram(SDRAM0_B0CR, sdram0_b0cr);
 	mtsdram(SDRAM0_B1CR, sdram0_b1cr);
 #ifndef CONFIG_405EP /* not on PPC405EP */
 	mtsdram(SDRAM0_B2CR, sdram0_b2cr);
 	mtsdram(SDRAM0_B3CR, sdram0_b3cr);
 #endif
 	mtsdram(SDRAM0_TR, sdram0_tr);

 	/* SDRAM have a power on delay,	 500 micro should do */
 	udelay(500);
 	sdram0_cfg = SDRAM0_CFG_DCE | SDRAM0_CFG_BRPF(1) | SDRAM0_CFG_ECCDD | SDRAM0_CFG_EMDULR;
 #ifndef CONFIG_405EP /* not on PPC405EP */
 	if (ecc_on)
 		sdram0_cfg |= SDRAM0_CFG_MEMCHK;
 #endif
 	mtsdram(SDRAM0_CFG, sdram0_cfg);

 	return (total_size);
 }

 int spd_read(uint addr)
 {
 	uchar data[2];

 	if (i2c_read(SPD_EEPROM_ADDRESS, addr, 1, data, 1) == 0)
 		return (int)data[0];
 	else
 		return 0;
 }

 #endif /* CONFIG_SPD_EEPROM */
	/*
	* arch/powerpc/cpu/ppc4xx/40x_spd_sdram.c
	* This SPD SDRAM detection code supports IBM/AMCC PPC44x cpu with a
	* SDRAM controller. Those are all current 405 PPC's.
	*
	* (C) Copyright 2001
	* Bill Hunter, Wave 7 Optics, williamhunter@attbi.com
	*
	* Based on code by:
	*
	* Kenneth Johansson ,Ericsson AB.
	* kenneth.johansson@etx.ericsson.se
	*
	* hacked up by bill hunter. fixed so we could run before
	* serial_init and console_init. previous version avoided this by
	* running out of cache memory during serial/console init, then running
	* this code later.
	*
	* (C) Copyright 2002
	* Jun Gu, Artesyn Technology, jung@artesyncp.com
	* Support for AMCC 440 based on OpenBIOS draminit.c from IBM.
	*
	* (C) Copyright 2005
	* Stefan Roese, DENX Software Engineering, sr@denx.de.
	*
	* See file CREDITS for list of people who contributed to this
	* project.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation; either version 2 of
	* the License, or (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
	* MA 02111-1307 USA
	*/

	#include <common.h>
	#include <asm/processor.h>
	#include <i2c.h>
	#include <asm/ppc4xx.h>

	#if defined(CONFIG_SPD_EEPROM) && !defined(CONFIG_440)

	/*
	* Set default values
	*/
	#ifndef CONFIG_SYS_I2C_SPEED
	#define CONFIG_SYS_I2C_SPEED 50000
	#endif

	#define ONE_BILLION 1000000000

	#define SDRAM0_CFG_DCE 0x80000000
	#define SDRAM0_CFG_SRE 0x40000000
	#define SDRAM0_CFG_PME 0x20000000
	#define SDRAM0_CFG_MEMCHK 0x10000000
	#define SDRAM0_CFG_REGEN 0x08000000
	#define SDRAM0_CFG_ECCDD 0x00400000
	#define SDRAM0_CFG_EMDULR 0x00200000
	#define SDRAM0_CFG_DRW_SHIFT (31-6)
	#define SDRAM0_CFG_BRPF_SHIFT (31-8)

	#define SDRAM0_TR_CASL_SHIFT (31-8)
	#define SDRAM0_TR_PTA_SHIFT (31-13)
	#define SDRAM0_TR_CTP_SHIFT (31-15)
	#define SDRAM0_TR_LDF_SHIFT (31-17)
	#define SDRAM0_TR_RFTA_SHIFT (31-29)
	#define SDRAM0_TR_RCD_SHIFT (31-31)

	#define SDRAM0_RTR_SHIFT (31-15)
	#define SDRAM0_ECCCFG_SHIFT (31-11)

	/* SDRAM0_CFG enable macro */
	#define SDRAM0_CFG_BRPF(x) ( ( x & 0x3)<< SDRAM0_CFG_BRPF_SHIFT )

	#define SDRAM0_BXCR_SZ_MASK 0x000e0000
	#define SDRAM0_BXCR_AM_MASK 0x0000e000

	#define SDRAM0_BXCR_SZ_SHIFT (31-14)
	#define SDRAM0_BXCR_AM_SHIFT (31-18)

	#define SDRAM0_BXCR_SZ(x) ( (( x << SDRAM0_BXCR_SZ_SHIFT) & SDRAM0_BXCR_SZ_MASK) )
	#define SDRAM0_BXCR_AM(x) ( (( x << SDRAM0_BXCR_AM_SHIFT) & SDRAM0_BXCR_AM_MASK) )

	#ifdef CONFIG_SPDDRAM_SILENT
	# define SPD_ERR(x) do { return 0; } while (0)
	#else
	# define SPD_ERR(x) do { printf(x); return(0); } while (0)
	#endif

	#define sdram_HZ_to_ns(hertz) (1000000000/(hertz))

	/* function prototypes */
	int spd_read(uint addr);


	/*
	* This function is reading data from the DIMM module EEPROM over the SPD bus
	* and uses that to program the sdram controller.
	*
	* This works on boards that has the same schematics that the AMCC walnut has.
	*
	* Input: null for default I2C spd functions or a pointer to a custom function
	* returning spd_data.
	*/

	long int spd_sdram(int(read_spd)(uint addr))
	{
	int tmp,row,col;
	int total_size,bank_size,bank_code;
	int mode;
	int bank_cnt;

	int sdram0_pmit=0x07c00000;
	int sdram0_b0cr;
	int sdram0_b1cr = 0;
	#ifndef CONFIG_405EP /* not on PPC405EP */
	int sdram0_b2cr = 0;
	int sdram0_b3cr = 0;
	int sdram0_besr0 = -1;
	int sdram0_besr1 = -1;
	int sdram0_eccesr = -1;
	int sdram0_ecccfg;
	int ecc_on;
	#endif

	int sdram0_rtr=0;
	int sdram0_tr=0;

	int sdram0_cfg=0;

	int t_rp;
	int t_rcd;
	int t_ras;
	int t_rc;
	int min_cas;

	PPC4xx_SYS_INFO sys_info;
	unsigned long bus_period_x_10;

	/*
	* get the board info
	*/
	get_sys_info(&sys_info);
	bus_period_x_10 = ONE_BILLION / (sys_info.freqPLB / 10);

	if (read_spd == 0){
	read_spd=spd_read;
	/*
	* Make sure I2C controller is initialized
	* before continuing.
	*/
	i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
	}

	/* Make shure we are using SDRAM */
	if (read_spd(2) != 0x04) {
	SPD_ERR("SDRAM - non SDRAM memory module found\n");
	}

	/* ------------------------------------------------------------------
	* configure memory timing register
	*
	* data from DIMM:
	* 27 IN Row Precharge Time ( t RP)
	* 29 MIN RAS to CAS Delay ( t RCD)
	* 127 Component and Clock Detail ,clk0-clk3, junction temp, CAS
	* -------------------------------------------------------------------*/

	/*
	* first figure out which cas latency mode to use
	* use the min supported mode
	*/

	tmp = read_spd(127) & 0x6;
	if (tmp == 0x02) { /* only cas = 2 supported */
	min_cas = 2;
	/* t_ck = read_spd(9); */
	/* t_ac = read_spd(10); */
	} else if (tmp == 0x04) { /* only cas = 3 supported */
	min_cas = 3;
	/* t_ck = read_spd(9); */
	/* t_ac = read_spd(10); */
	} else if (tmp == 0x06) { /* 2,3 supported, so use 2 */
	min_cas = 2;
	/* t_ck = read_spd(23); */
	/* t_ac = read_spd(24); */
	} else {
	SPD_ERR("SDRAM - unsupported CAS latency \n");
	}

	/* get some timing values, t_rp,t_rcd,t_ras,t_rc
	*/
	t_rp = read_spd(27);
	t_rcd = read_spd(29);
	t_ras = read_spd(30);
	t_rc = t_ras + t_rp;

	/* The following timing calcs subtract 1 before deviding.
	* this has effect of using ceiling instead of floor rounding,
	* and also subtracting 1 to convert number to reg value
	*/
	/* set up CASL */
	sdram0_tr = (min_cas - 1) << SDRAM0_TR_CASL_SHIFT;
	/* set up PTA */
	sdram0_tr \|= ((((t_rp - 1) * 10)/bus_period_x_10) & 0x3) << SDRAM0_TR_PTA_SHIFT;
	/* set up CTP */
	tmp = (((t_rc - t_rcd - t_rp -1) * 10) / bus_period_x_10) & 0x3;
	if (tmp < 1)
	tmp = 1;
	sdram0_tr \|= tmp << SDRAM0_TR_CTP_SHIFT;
	/* set LDF = 2 cycles, reg value = 1 */
	sdram0_tr \|= 1 << SDRAM0_TR_LDF_SHIFT;
	/* set RFTA = t_rfc/bus_period, use t_rfc = t_rc */
	tmp = (((t_rc - 1) * 10) / bus_period_x_10) - 3;
	if (tmp < 0)
	tmp = 0;
	if (tmp > 6)
	tmp = 6;
	sdram0_tr \|= tmp << SDRAM0_TR_RFTA_SHIFT;
	/* set RCD = t_rcd/bus_period*/
	sdram0_tr \|= ((((t_rcd - 1) * 10) / bus_period_x_10) &0x3) << SDRAM0_TR_RCD_SHIFT ;


	/*------------------------------------------------------------------
	* configure RTR register
	* -------------------------------------------------------------------*/
	row = read_spd(3);
	col = read_spd(4);
	tmp = read_spd(12) & 0x7f ; /* refresh type less self refresh bit */
	switch (tmp) {
	case 0x00:
	tmp = 15625;
	break;
	case 0x01:
	tmp = 15625 / 4;
	break;
	case 0x02:
	tmp = 15625 / 2;
	break;
	case 0x03:
	tmp = 15625 * 2;
	break;
	case 0x04:
	tmp = 15625 * 4;
	break;
	case 0x05:
	tmp = 15625 * 8;
	break;
	default:
	SPD_ERR("SDRAM - Bad refresh period \n");
	}
	/* convert from nsec to bus cycles */
	tmp = (tmp * 10) / bus_period_x_10;
	sdram0_rtr = (tmp & 0x3ff8) << SDRAM0_RTR_SHIFT;

	/*------------------------------------------------------------------
	* determine the number of banks used
	* -------------------------------------------------------------------*/
	/* byte 7:6 is module data width */
	if (read_spd(7) != 0)
	SPD_ERR("SDRAM - unsupported module width\n");
	tmp = read_spd(6);
	if (tmp < 32)
	SPD_ERR("SDRAM - unsupported module width\n");
	else if (tmp < 64)
	bank_cnt = 1; /* one bank per sdram side */
	else if (tmp < 73)
	bank_cnt = 2; /* need two banks per side */
	else if (tmp < 161)
	bank_cnt = 4; /* need four banks per side */
	else
	SPD_ERR("SDRAM - unsupported module width\n");

	/* byte 5 is the module row count (refered to as dimm "sides") */
	tmp = read_spd(5);
	if (tmp == 1)
	;
	else if (tmp==2)
	bank_cnt *= 2;
	else if (tmp==4)
	bank_cnt *= 4;
	else
	bank_cnt = 8; /* 8 is an error code */

	if (bank_cnt > 4) /* we only have 4 banks to work with */
	SPD_ERR("SDRAM - unsupported module rows for this width\n");

	#ifndef CONFIG_405EP /* not on PPC405EP */
	/* now check for ECC ability of module. We only support ECC
	* on 32 bit wide devices with 8 bit ECC.
	*/
	if ((read_spd(11)==2) && (read_spd(6)==40) && (read_spd(14)==8)) {
	sdram0_ecccfg = 0xf << SDRAM0_ECCCFG_SHIFT;
	ecc_on = 1;
	} else {
	sdram0_ecccfg = 0;
	ecc_on = 0;
	}
	#endif

	/*------------------------------------------------------------------
	* calculate total size
	* -------------------------------------------------------------------*/
	/* calculate total size and do sanity check */
	tmp = read_spd(31);
	total_size = 1 << 22; /* total_size = 4MB */
	/* now multiply 4M by the smallest device row density */
	/* note that we don't support asymetric rows */
	while (((tmp & 0x0001) == 0) && (tmp != 0)) {
	total_size = total_size << 1;
	tmp = tmp >> 1;
	}
	total_size = read_spd(5); / mult by module rows (dimm sides) */

	/*------------------------------------------------------------------
	* map rows * cols * banks to a mode
	* -------------------------------------------------------------------*/

	switch (row) {
	case 11:
	switch (col) {
	case 8:
	mode=4; /* mode 5 */
	break;
	case 9:
	case 10:
	mode=0; /* mode 1 */
	break;
	default:
	SPD_ERR("SDRAM - unsupported mode\n");
	}
	break;
	case 12:
	switch (col) {
	case 8:
	mode=3; /* mode 4 */
	break;
	case 9:
	case 10:
	mode=1; /* mode 2 */
	break;
	default:
	SPD_ERR("SDRAM - unsupported mode\n");
	}
	break;
	case 13:
	switch (col) {
	case 8:
	mode=5; /* mode 6 */
	break;
	case 9:
	case 10:
	if (read_spd(17) == 2)
	mode = 6; /* mode 7 */
	else
	mode = 2; /* mode 3 */
	break;
	case 11:
	mode = 2; /* mode 3 */
	break;
	default:
	SPD_ERR("SDRAM - unsupported mode\n");
	}
	break;
	default:
	SPD_ERR("SDRAM - unsupported mode\n");
	}

	/*------------------------------------------------------------------
	* using the calculated values, compute the bank
	* config register values.
	* -------------------------------------------------------------------*/

	/* compute the size of each bank */
	bank_size = total_size / bank_cnt;
	/* convert bank size to bank size code for ppc4xx
	by takeing log2(bank_size) - 22 */
	tmp = bank_size; /* start with tmp = bank_size */
	bank_code = 0; /* and bank_code = 0 */
	while (tmp > 1) { /* this takes log2 of tmp */
	bank_code++; /* and stores result in bank_code */
	tmp = tmp >> 1;
	} /* bank_code is now log2(bank_size) */
	bank_code -= 22; /* subtract 22 to get the code */

	tmp = SDRAM0_BXCR_SZ(bank_code) \| SDRAM0_BXCR_AM(mode) \| 1;
	sdram0_b0cr = (bank_size * 0) \| tmp;
	#ifndef CONFIG_405EP /* not on PPC405EP */
	if (bank_cnt > 1)
	sdram0_b2cr = (bank_size * 1) \| tmp;
	if (bank_cnt > 2)
	sdram0_b1cr = (bank_size * 2) \| tmp;
	if (bank_cnt > 3)
	sdram0_b3cr = (bank_size * 3) \| tmp;
	#else
	/* PPC405EP chip only supports two SDRAM banks */
	if (bank_cnt > 1)
	sdram0_b1cr = (bank_size * 1) \| tmp;
	if (bank_cnt > 2)
	total_size = 2 * bank_size;
	#endif

	/*
	* enable sdram controller DCE=1
	* enable burst read prefetch to 32 bytes BRPF=2
	* leave other functions off
	*/

	/*------------------------------------------------------------------
	* now that we've done our calculations, we are ready to
	* program all the registers.
	* -------------------------------------------------------------------*/

	/* disable memcontroller so updates work */
	mtsdram(SDRAM0_CFG, 0);

	#ifndef CONFIG_405EP /* not on PPC405EP */
	mtsdram(SDRAM0_BESR0, sdram0_besr0);
	mtsdram(SDRAM0_BESR1, sdram0_besr1);
	mtsdram(SDRAM0_ECCCFG, sdram0_ecccfg);
	mtsdram(SDRAM0_ECCESR, sdram0_eccesr);
	#endif
	mtsdram(SDRAM0_RTR, sdram0_rtr);
	mtsdram(SDRAM0_PMIT, sdram0_pmit);
	mtsdram(SDRAM0_B0CR, sdram0_b0cr);
	mtsdram(SDRAM0_B1CR, sdram0_b1cr);
	#ifndef CONFIG_405EP /* not on PPC405EP */
	mtsdram(SDRAM0_B2CR, sdram0_b2cr);
	mtsdram(SDRAM0_B3CR, sdram0_b3cr);
	#endif
	mtsdram(SDRAM0_TR, sdram0_tr);

	/* SDRAM have a power on delay, 500 micro should do */
	udelay(500);
	sdram0_cfg = SDRAM0_CFG_DCE \| SDRAM0_CFG_BRPF(1) \| SDRAM0_CFG_ECCDD \| SDRAM0_CFG_EMDULR;
	#ifndef CONFIG_405EP /* not on PPC405EP */
	if (ecc_on)
	sdram0_cfg \|= SDRAM0_CFG_MEMCHK;
	#endif
	mtsdram(SDRAM0_CFG, sdram0_cfg);

	return (total_size);
	}

	int spd_read(uint addr)
	{
	uchar data[2];

	if (i2c_read(SPD_EEPROM_ADDRESS, addr, 1, data, 1) == 0)
	return (int)data[0];
	else
	return 0;
	}

	#endif /* CONFIG_SPD_EEPROM */