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Allow arch-specific setting of global_data in board_init_f_mem()

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At present we have a simple assignment to gd. With some archs this is
implemented as a register or through some other means; a simple assignment
does not suit in all cases.

Change this to a function and add documentation to describe how this all
works.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: York Sun <yorksun@freescale.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Simon Glass 2015-08-10 20:44:30 -06:00
parent 2afddae075
commit 1fed87db6a
2 changed files with 54 additions and 2 deletions
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13
common/board_f.c
View file

@ -1027,16 +1027,25 @@ void board_init_f_r(void)
}
#endif /* CONFIG_X86 */
/* Unfortunately x86 can't compile this code as gd cannot be assigned */
#ifndef CONFIG_X86
__weak void arch_setup_gd(struct global_data *gd_ptr)
{
gd = gd_ptr;
}
ulong board_init_f_mem(ulong top)
{
struct global_data *gd_ptr;
/* Leave space for the stack we are running with now */
top -= 0x40;
top -= sizeof(struct global_data);
top = ALIGN(top, 16);
gd = (struct global_data *)top;
memset((void *)gd, '\0', sizeof(*gd));
gd_ptr = (struct global_data *)top;
memset(gd_ptr, '\0', sizeof(*gd));
arch_setup_gd(gd_ptr);
#ifdef CONFIG_SYS_MALLOC_F_LEN
top -= CONFIG_SYS_MALLOC_F_LEN;

43
include/common.h
View file

@ -217,6 +217,49 @@ extern char console_buffer[];
/* arch/$(ARCH)/lib/board.c */
void board_init_f(ulong);
void board_init_r(gd_t *, ulong) __attribute__ ((noreturn));
/**
* board_init_f_mem() - Allocate global data and set stack position
*
* This function is called by each architecture very early in the start-up
* code to set up the environment for board_init_f(). It allocates space for
* global_data (see include/asm-generic/global_data.h) and places the stack
* below this.
*
* This function requires a stack[1] Normally this is at @top. The function
* starts allocating space from 64 bytes below @top. First it creates space
* for global_data. Then it calls arch_setup_gd() which sets gd to point to
* the global_data space and can reserve additional bytes of space if
* required). Finally it allocates early malloc() memory
* (CONFIG_SYS_MALLOC_F_LEN). The new top of the stack is just below this,
* and it returned by this function.
*
* [1] Strictly speaking it would be possible to implement this function
* in C on many archs such that it does not require a stack. However this
* does not seem hugely important as only 64 byte are wasted. The 64 bytes
* are used to handle the calling standard which generally requires pushing
* addresses or registers onto the stack. We should be able to get away with
* less if this becomes important.
*
* @top: Top of available memory, also normally the top of the stack
* @return: New stack location
*/
ulong board_init_f_mem(ulong top);
/**
* arch_setup_gd() - Set up the global_data pointer
*
* This pointer is special in some architectures and cannot easily be assigned
* to. For example on x86 it is implemented by adding a specific record to its
* Global Descriptor Table! So we we provide a function to carry out this task.
* For most architectures this can simply be:
*
* gd = gd_ptr;
*
* @gd_ptr: Pointer to global data
*/
void arch_setup_gd(gd_t *gd_ptr);
int checkboard(void);
int show_board_info(void);
int checkflash(void);