On Tue, Aug 11, 2015 at 10:44 AM, Simon Glass sjg@chromium.org wrote:
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
Changes in v2:
- Drop unused 'reserve_size' argument
- Rename arch_setup_gdt() to arch_setup_gd()
- Expand the comment about the 64-byte stack space
- Fix a comma which should be a period
- Add a comment as to why we can't compile the weak arch_setup_gd() on x86
common/board_f.c | 13 +++++++++++-- include/common.h | 43 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 54 insertions(+), 2 deletions(-)
diff --git a/common/board_f.c b/common/board_f.c index 74f77f1..37b7bf5 100644 --- a/common/board_f.c +++ b/common/board_f.c @@ -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; diff --git a/include/common.h b/include/common.h index fcc9ae7..48e5006 100644 --- a/include/common.h +++ b/include/common.h @@ -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); --
Reviewed-by: Bin Meng bmeng.cn@gmail.com