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Loading the kernel with TFTP and U-boot

03 Jan

Hello again.

In this post we are going to try to load the kernel using TFTP and then load the root file system using NFS. I explained how to compile u-boot source in a previous post. We should make some slight changes to it.

Prerequisites

  1. Connect QEMU to network
  2. NFS root file system on host
$ sudo apt-get install tftpd-hpa
$ sudo apt-get install tftp

I suppose you have downloaded the latest source code of u-boot from this link. Extract the file and go into the folder.

$ gedit include/configs/versatile.h

Let’s start with modifying the content of versatile header file. You can change the whole file content with the one I provided below. Because we are going to use network.

/*
 * (C) Copyright 2003
 * Texas Instruments.
 * Kshitij Gupta <kshitij@ti.com>
 * Configuation settings for the TI OMAP Innovator board.
 *
 * (C) Copyright 2004
 * ARM Ltd.
 * Philippe Robin, <philippe.robin@arm.com>
 * Configuration for Versatile PB.
 *
 * 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
 */

#ifndef __CONFIG_H
#define __CONFIG_H

#define CONFIG_ARCH_VERSATILE_QEMU
/*
 * High Level Configuration Options
 * (easy to change)
 */
#define CONFIG_ARM926EJS	1	/* This is an arm926ejs CPU core */
#define CONFIG_VERSATILE	1	/* in Versatile Platform Board	*/
#define CONFIG_ARCH_VERSATILE	1	/* Specifically, a Versatile	*/

#define CONFIG_SYS_MEMTEST_START	0x100000
#define CONFIG_SYS_MEMTEST_END		0x10000000
#define CONFIG_SYS_HZ			(1000000 / 256)
#define CONFIG_SYS_TIMERBASE		0x101E2000	/* Timer 0 and 1 base */

#define CONFIG_SYS_TIMER_INTERVAL	10000
#define CONFIG_SYS_TIMER_RELOAD		(CONFIG_SYS_TIMER_INTERVAL >> 4)
#define CONFIG_SYS_TIMER_CTRL		0x84		/* Enable, Clock / 16 */

/*
 * control registers
 */
#define VERSATILE_SCTL_BASE		0x101E0000	/* System controller */

/*
 * System controller bit assignment
 */
#define VERSATILE_REFCLK	0
#define VERSATILE_TIMCLK	1

#define VERSATILE_TIMER1_EnSel	15
#define VERSATILE_TIMER2_EnSel	17
#define VERSATILE_TIMER3_EnSel	19
#define VERSATILE_TIMER4_EnSel	21

#define CONFIG_CMDLINE_TAG		1	/* enable passing of ATAGs */
#define CONFIG_SETUP_MEMORY_TAGS	1
#define CONFIG_MISC_INIT_R		1
/*
 * Size of malloc() pool
 */
#define CONFIG_ENV_SIZE			8192
#define CONFIG_SYS_MALLOC_LEN		(CONFIG_ENV_SIZE + 128 * 1024)

/*
 * Hardware drivers
 */

#define CONFIG_SMC91111
#define CONFIG_SMC_USE_32_BIT
#define CONFIG_SMC91111_BASE	0x10010000
//#undef CONFIG_SMC91111_EXT_PHY
#define CONFIG_SMC91111_EXT_PHY

/*
 * NS16550 Configuration
 */
#define CONFIG_PL011_SERIAL
#define CONFIG_PL011_CLOCK	24000000
#define CONFIG_PL01x_PORTS				\
			{(void *)CONFIG_SYS_SERIAL0,	\
			 (void *)CONFIG_SYS_SERIAL1 }
#define CONFIG_CONS_INDEX	0

#define CONFIG_BAUDRATE			38400
#define CONFIG_SYS_SERIAL0		0x101F1000
#define CONFIG_SYS_SERIAL1		0x101F2000

/*
 * Command line configuration.
 */
#define CONFIG_CMD_BDI
#define CONFIG_CMD_DHCP
#define CONFIG_CMD_FLASH
#define CONFIG_CMD_IMI
#define CONFIG_CMD_MEMORY
#define CONFIG_CMD_NET
#define CONFIG_CMD_PING
#define CONFIG_CMD_SAVEENV

/*
 * BOOTP options
 */
#define CONFIG_BOOTCOMMAND "setenv autoload no; dhcp; setenv serverip 192.168.2.135; tftpboot 0x7FC0 uImage; bootm 0x7FC0"
#define CONFIG_BOOTP_BOOTPATH
#define CONFIG_BOOTP_GATEWAY	192.168.2.1
#define CONFIG_BOOTP_HOSTNAME
#define CONFIG_BOOTP_SUBNETMASK	255.255.255.0
#define CONFIG_IPADDR		192.168.2.116
#define CONFIG_NETMASK   	255.255.255.0
#define CONFIG_SERVERIP  	192.168.32.135

#define CONFIG_BOOTDELAY	5
/*
 *#define CONFIG_BOOTARGS		"root=/dev/nfs mem=128M ip=dhcp "\
 *				"netdev=25,0,0xf1010000,0xf1010010,eth0"
 */
#define CONFIG_BOOTARGS		"root=/dev/nfs mem=128M nfsroot=192.168.2.135:/srv/nfs/_install rw ip=dhcp"
/*
 * Static configuration when assigning fixed address
 */
#define CONFIG_BOOTFILE		"uImage" /* file to load */

/*
 * Miscellaneous configurable options
 */
#define CONFIG_SYS_LONGHELP	/* undef to save memory */
#define CONFIG_SYS_CBSIZE	256		/* Console I/O Buffer Size */
/* Monitor Command Prompt	 */
#ifdef CONFIG_ARCH_VERSATILE_AB
# define CONFIG_SYS_PROMPT	"VersatileAB # "
#else
# define CONFIG_SYS_PROMPT	"Emreboy # "
#endif
/* Print Buffer Size */
#define CONFIG_SYS_PBSIZE	\
			(CONFIG_SYS_CBSIZE + sizeof(CONFIG_SYS_PROMPT) + 16)
#define CONFIG_SYS_MAXARGS	16		/* max number of command args */
#define CONFIG_SYS_BARGSIZE	CONFIG_SYS_CBSIZE /* Boot Argument Buffer Size */

#define CONFIG_SYS_LOAD_ADDR	0x7fc0	/* default load address */

/*-----------------------------------------------------------------------
 * Physical Memory Map
 */
#define CONFIG_NR_DRAM_BANKS	1	/* we have 1 bank of DRAM */
#define PHYS_SDRAM_1		0x00000000	/* SDRAM Bank #1 */
#define PHYS_SDRAM_1_SIZE	0x08000000	/* 128 MB */
#define PHYS_FLASH_SIZE		0x04000000	/* 64MB */

#define CONFIG_SYS_SDRAM_BASE		PHYS_SDRAM_1
#define CONFIG_SYS_INIT_RAM_ADDR	0x00800000
#define CONFIG_SYS_INIT_RAM_SIZE	0x000FFFFF
#define CONFIG_SYS_GBL_DATA_OFFSET	(CONFIG_SYS_INIT_RAM_SIZE - \
						GENERATED_GBL_DATA_SIZE)
#define CONFIG_SYS_INIT_SP_ADDR	(CONFIG_SYS_INIT_RAM_ADDR + \
						CONFIG_SYS_GBL_DATA_OFFSET)

#define CONFIG_BOARD_EARLY_INIT_F

/*-----------------------------------------------------------------------
 * FLASH and environment organization
 */
#ifdef CONFIG_ARCH_VERSATILE_QEMU
#define CONFIG_SYS_TEXT_BASE		0x10000
#define CONFIG_SYS_NO_FLASH
#define CONFIG_ENV_IS_NOWHERE
#define CONFIG_SYS_MONITOR_LEN		0x80000
#else
#define CONFIG_SYS_TEXT_BASE		0x01000000
/*
 * Use the CFI flash driver for ease of use
 */
#define CONFIG_SYS_FLASH_CFI
#define CONFIG_FLASH_CFI_DRIVER
#define CONFIG_ENV_IS_IN_FLASH	1
/*
 *	System control register
 */
#define VERSATILE_SYS_BASE		0x10000000
#define VERSATILE_SYS_FLASH_OFFSET	0x4C
#define VERSATILE_FLASHCTRL		\
		(VERSATILE_SYS_BASE + VERSATILE_SYS_FLASH_OFFSET)
/* Enable writing to flash */
#define VERSATILE_FLASHPROG_FLVPPEN	(1 << 0)

/* timeout values are in ticks */
#define CONFIG_SYS_FLASH_ERASE_TOUT	(2 * CONFIG_SYS_HZ) /* Erase Timeout */
#define CONFIG_SYS_FLASH_WRITE_TOUT	(2 * CONFIG_SYS_HZ) /* Write Timeout */

/*
 * Note that CONFIG_SYS_MAX_FLASH_SECT allows for a parameter block
 * i.e.
 *	the bottom "sector" (bottom boot), or top "sector"
 *	(top boot), is a seperate erase region divided into
 *	4 (equal) smaller sectors. This, notionally, allows
 *	quicker erase/rewrire of the most frequently changed
 *	area......
 *	CONFIG_SYS_MAX_FLASH_SECT is padded up to a multiple of 4
 */

#ifdef CONFIG_ARCH_VERSATILE_AB
#define FLASH_SECTOR_SIZE		0x00020000	/* 128 KB sectors */
#define CONFIG_ENV_SECT_SIZE		(2 * FLASH_SECTOR_SIZE)
#define CONFIG_SYS_MAX_FLASH_SECT	(520)
#endif

#ifdef CONFIG_ARCH_VERSATILE_PB		/* Versatile PB is default	*/
#define FLASH_SECTOR_SIZE		0x00040000	/* 256 KB sectors */
#define CONFIG_ENV_SECT_SIZE		FLASH_SECTOR_SIZE
#define CONFIG_SYS_MAX_FLASH_SECT	(260)
#endif

#define CONFIG_SYS_FLASH_BASE		0x34000000
#define CONFIG_SYS_MAX_FLASH_BANKS	1

#define CONFIG_SYS_MONITOR_LEN		(4 * CONFIG_ENV_SECT_SIZE)

/* The ARM Boot Monitor is shipped in the lowest sector of flash */

#define FLASH_TOP			(CONFIG_SYS_FLASH_BASE + PHYS_FLASH_SIZE)
#define CONFIG_ENV_ADDR			(FLASH_TOP - CONFIG_ENV_SECT_SIZE)
#define CONFIG_ENV_OFFSET		(CONFIG_ENV_ADDR - CONFIG_SYS_FLASH_BASE)
#define CONFIG_SYS_MONITOR_BASE		(CONFIG_ENV_ADDR - CONFIG_SYS_MONITOR_LEN)

#define CONFIG_SYS_FLASH_PROTECTION	/* The devices have real protection */
#define CONFIG_SYS_FLASH_EMPTY_INFO	/* flinfo indicates empty blocks */

#endif

#endif	/* __CONFIG_H */

Just change the ip addresses according to your network configuration. Note that I commented out the line “#undef CONFIG_SMC91111_EXT_PHY” and instad changed it as “#define”. In the first case u-boot worked too slow on QEMU when the dhcp or tftpboot commands were executed.
Now save the file and close it.

$ make CROSS_COMPILE=arm-linux- clean
$ make versatileqemu_config ARCH=arm CROSS_COMPILE=arm-linux-
$ make all ARCH=arm CROSS_COMPILE=arm-linux-
$ ll -h u-boot.bin

Now we have our u-boot.bin file.

In the kernel source folder create a uImage (kernel image with a u-boot header) if you did not before.

$ make ARCH=arm CROSS_COMPILE=arm-linux- uImage

Let’s configure the TFTP stuff. I hope you all downloaded the packages I specified in the Prerequisites part. Start the TFTP daemon.

$ sudo service tftpd-hpa start

Copy the uImage file to the tftpboot folder.

$ sudo cp linux-3.7.1/arch/arm/boot/uImage /var/lib/tftpboot

First of all make sure that your tftp server works fine.

$ tftp localhost
> get uImage
> quit
$ ll -h uImage

Now start QEMU.

$ sudo /etc/qemu-ifup tap0
$ sudo qemu-system-arm -M versatilepb -m 128M -kernel u-boot.bin -net nic -net tap,ifname=tap0,script=no,downscript=no

When QEMU starts press “CTRL-ALT-3” key combination to see the serial console on QEMU. If everything is OK the U-BOOT must be working. You can see the environment variables by typing “printenv”
We had assigned the bootargs variable in the versatile.h file. Just check it. It’s important because when we boot the kernel these arguments will be passed to the kernel to mount the root file system using NFS.

I’m going to use DHCP to assign the IP numbers and other network variables. Type the commands below in the given order. The order is crucial because DHCP assigns a different address to “serverip” variable (that of “gatewayip”) and we need to correct it. We are also setting the “autoload” variable the value “no”. We don’t the dhcp command to load the kernel since it won’t be able to because as I have just mentioned dhcp assigns a different IP number to “serverip”. (Do not forget to assign your own host IP number to serverip. NOT MINE!)

On QEMU u-boot command prompt type:

# setenv autoload no
# dhcp
# setenv serverip 192.168.2.135
# tftpboot
# bootm 0x7FC0

In my case the tftpboot command copied the kernel image to the address 0x7FC0. Yours might be different. Act accordingly.
Press “CTRL-ALT-1” key combination to pass to the boot scren on QEMU. If all went all right you must see the boot messages and finally the root file system being mounted.

u-boot

Kernel boot

 
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Posted by on January 3, 2013 in Linux

 

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