[U-Boot] Where I'm going with x86 board.c

[Graeme Russ]

Hi Simon,

On 22/12/11 17:44, Simon Glass wrote:
> Hi Graeme,
> 
> On Tue, Dec 20, 2011 at 4:06 AM, Graeme Russ <graeme.russ at gmail.com> wrote:
>> With Simon's work on generic relocation support, I thought I would throw in
>> what I am planning for arch/x86/lib/board.c
>>
>> Now this is not a patch, it is a work-in-progress complete version of the
>> file (compiles, will test soon) - If feedback is positive, I'll add this to
>> an upcoming patch set
> 
> Looks good to me+++

Thanks for having a look :)

>> Notice the amount of wrapping around void functions - If all other arch's
>> follow this lead, most of this wrapping can be removed by changing the
>> function signatures.
>>
>> Lines 428 - 585 are effectively the generic init sequence - The rest is
>> wrappers, init sequence arrays, or fluff that should be moved
>>
>> I noticed something along the way - gd is no longer special... let me
>> explain...
>>
>> Some arch's use a dedicated register for the gd pointer - This allows the
>> pointer to be written to prior to relocation. For x86, the gd pointer is
>> simply passed around as a function parameter early - If the init_sequence_f
>> functions accepted a gd pointer as a parameter, there would be no need for
>> it to be global prior to relocation and therefore no need to allocate a
>> permanent register for it - Of course do_init_loop() would no longer be
>> generic for both pre and post relocation. This does mess with the
>> stand-alone API, but as discussed before, stand alone applications should
>> not be accessing gd anyway, so there should be no API to break ;)
> 
> Actually as it happens I did a bit of an experiment with this some
> weeks ago and my original board stuff had gd as a parameter for the
> pre-reloc functions (some with stubs to other ones like
> console_init_f()). On ARM it really doesn't make a lot of sense to use
> a global variable instead of a parameter. I decided that it was a bit
> much to bite off in one go :-) Partly that was because IMO gd really
> only makes sense prior to relocation - for the post-relocation init
> calls they don't have a lot of need for gd.

I don't think this is 100% correct - I'm sure gd is used all over the place
post init

> So it has my vote. Once I get somewhere on the reboard series I will
> post my common/board.c. As I may have mentioned I have elected so far
> to leave the initcall list and local functions in
> arch/xxx/lib/board.c.
> 
> Would be good to get all this moving.

Well, I have a more thorough patch in the making - I creates
init_wrappers.c and init_helpers.c and board.c collapses very dramatically
(see below) - with a lot of #ifdef hell...

Notice the new board_init_f_r() - This is where U-Boot is running from
Flash, but SDRAM has been initialised and the stack is now in RAM - So this
is where we move gd to RAM and perform relocation. As a bonus, relocation
can be done with cache enabled :)

Regards,

Graeme



/*
 * (C) Copyright 2008-2011
 * Graeme Russ, <graeme.russ at gmail.com>
 *
 * (C) Copyright 2002
 * Daniel Engström, Omicron Ceti AB, <daniel at omicron.se>
 *
 * (C) Copyright 2002
 * Wolfgang Denk, DENX Software Engineering, <wd at denx.de>
 *
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
 * Marius Groeger <mgroeger at sysgo.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 <watchdog.h>
#include <stdio_dev.h>
#include <asm/u-boot-x86.h>

#include <asm/init_helpers.h>
#include <asm/init_wrappers.h>

/*
 * Pointer to initial global data area
 *
 * Here we initialize it.
 */
#undef	XTRN_DECLARE_GLOBAL_DATA_PTR
#define XTRN_DECLARE_GLOBAL_DATA_PTR	/* empty = allocate here */
DECLARE_GLOBAL_DATA_PTR = (gd_t *) (CONFIG_SYS_INIT_GD_ADDR);

/*
 * Breath some life into the board...
 *
 * Initialize an SMC for serial comms, and carry out some hardware
 * tests.
 *
 * The first part of initialization is running from Flash memory;
 * its main purpose is to initialize the RAM so that we
 * can relocate the monitor code to RAM.
 */

/*
 * All attempts to come up with a "common" initialization sequence
 * that works for all boards and architectures failed: some of the
 * requirements are just _too_ different. To get rid of the resulting
 * mess of board dependend #ifdef'ed code we now make the whole
 * initialization sequence configurable to the user.
 *
 * The requirements for any new initalization function is simple: it
 * receives a pointer to the "global data" structure as it's only
 * argument, and returns an integer return code, where 0 means
 * "continue" and != 0 means "fatal error, hang the system".
 */
typedef int (init_fnc_t) (void);

init_fnc_t *init_sequence_f[] = {
	cpu_init_f,
	board_early_init_f,
	env_init,
	init_baudrate_f,
	serial_init,
	console_init_f,
	dram_init_f,

	NULL,
};

init_fnc_t *init_sequence_r[] = {
	init_bd_struct_r,
	mem_malloc_init_r,
	cpu_init_r,
	board_early_init_r,
	dram_init,
	interrupt_init,
	timer_init,
	display_banner,
	display_dram_config,
#ifdef CONFIG_SERIAL_MULTI
	serial_initialize_r,
#endif
#ifndef CONFIG_SYS_NO_FLASH
	flash_init_r,
#endif
	env_relocate_r,
#ifdef CONFIG_CMD_NET
	init_ip_address_r,
#endif
#ifdef CONFIG_PCI
	pci_init_r,
#endif
	stdio_init,
	jumptable_init_r,
	console_init_r,
#ifdef CONFIG_MISC_INIT_R
	misc_init_r,
#endif
#if defined(CONFIG_CMD_PCMCIA) && !defined(CONFIG_CMD_IDE)
	pci_init_r,
#endif
#if defined(CONFIG_CMD_KGDB)
	kgdb_init_r,
#endif
	enable_interrupts_r,
#ifdef CONFIG_STATUS_LED
	status_led_set_r,
#endif
	set_load_addr_r,
#if defined(CONFIG_CMD_NET)
	set_bootfile_r,
#endif
#if defined(CONFIG_CMD_IDE)
	ide_init_r,
#endif
#if defined(CONFIG_CMD_SCSI)
	scsi_init_r,
#endif
#if defined(CONFIG_CMD_DOC)
	doc_init_r,
#endif
#ifdef CONFIG_BITBANGMII
	bb_miiphy_init_r,
#endif
#if defined(CONFIG_CMD_NET)
	eth_initialize_r,
#ifdef CONFIG_RESET_PHY_R
	reset_phy_r,
#endif
#endif
#ifdef CONFIG_LAST_STAGE_INIT
	last_stage_init,
#endif
	NULL,
};

static void do_init_loop(init_fnc_t **init_fnc_ptr)
{
	for (; *init_fnc_ptr; ++init_fnc_ptr) {
		WATCHDOG_RESET();
		if ((*init_fnc_ptr)() != 0)
			hang();
	}
}

/* Perform all steps necessary to get RAM initialised ready for relocation */
void board_init_f(ulong boot_flags)
{
	gd->flags = boot_flags;

	do_init_loop(init_sequence_f);

	/*
	 * SDRAM is now initialised setup a new stack in SDRAM
	 *
	 * Code execution will continue in Flash, but with the stack
	 * in SDRAM. This allows us to copy global data out of the CPU
	 * cache prior to copying U-Boot into RAM which means we can
	 * enable caching for the copy operation (which speeds it up
	 * considerably)
	 */
	move_stack_to_sdram(gd->ram_size);

	/* NOTREACHED - move_stack_to_sdram() does not return */
	while (1)
		;
}

void board_init_f_r(gd_t *id)
{
	/*
	 * U-Boot is running from flash, but the stack is now in SDRAM
	 * (id = top of stack = final location of global data)
	 */

	/*
	 * gd is still in CAR - Copy it into SDRAM
	 *
	 * NOTE: We cannot set the gd variable yet as it lives in .data
	 * which has not been relocated to RAM yet
	 */
	memcpy(id, gd, sizeof(gd_t));

	/* Initialise the CPU cache(s) */
	if (init_cache() != 0)
		hang();

	/* Copy U-Boot to RAM and resume code execution in RAM */
	relocate_code(0, id, 0);

	/* NOTREACHED - relocate_code() does not return */
	while (1)
		;
}

__attribute__ ((__noreturn__))
void board_init_r(gd_t *id, ulong dest_addr)
{
	/* Global data pointer is now writable */
	gd = id;

	gd->flags |= GD_FLG_RELOC;

	/* compiler optimization barrier needed for GCC >= 3.4 */
	__asm__ __volatile__("" : : : "memory");

	do_init_loop(init_sequence_r);

	/* main_loop() can return to retry autoboot, if so just run it again. */
	for (;;)
		main_loop();

	/* NOTREACHED - no way out of command loop except booting */
}

__attribute__ ((__noreturn__))
void hang(void)
{
	puts("### ERROR ### Please RESET the board ###\n");
	for (;;)
		;
}