Hi Simon & Bin,
On Tue, Jan 6, 2015 at 12:40 AM, Bin Meng bmeng.cn@gmail.com wrote:
Hi Simon,
On Mon, Jan 5, 2015 at 9:44 AM, Simon Glass sjg@chromium.org wrote:
Hi Bin,
On 3 January 2015 at 20:26, Bin Meng bmeng.cn@gmail.com wrote:
Hi Simon,
On Fri, Jan 2, 2015 at 6:23 AM, Simon Glass sjg@chromium.org wrote:
Hi Bin,
On 30 December 2014 at 22:51, Bin Meng bmeng.cn@gmail.com wrote:
Hi Simon,
On Sun, Dec 28, 2014 at 10:20 AM, Simon Glass sjg@chromium.org
wrote:
For bare platforms we turn off ROM-caching before calling
board_init_f_r()
It is then very slow to copy U-Boot from ROM to RAM. So adjust the
order so
that the copying happens before we turn off ROM-caching.
Signed-off-by: Simon Glass sjg@chromium.org
common/board_f.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/common/board_f.c b/common/board_f.c index 98c9c72..1b65575 100644 --- a/common/board_f.c +++ b/common/board_f.c @@ -983,6 +983,11 @@ static init_fnc_t init_sequence_f[] = { INIT_FUNC_WATCHDOG_RESET reloc_fdt, setup_reloc, +#ifdef CONFIG_X86
copy_uboot_to_ram,clear_bss,do_elf_reloc_fixups,+#endif #if !defined(CONFIG_ARM) && !defined(CONFIG_SANDBOX) jump_to_copy, #endif @@ -1042,9 +1047,6 @@ void board_init_f(ulong boot_flags) */ static init_fnc_t init_sequence_f_r[] = { init_cache_f_r,
copy_uboot_to_ram,clear_bss,do_elf_reloc_fixups, NULL,};
Wow, doesn't this bring back some memories. I've had a look over this code as it is now and it took a while to sink in. Things have moved on in the past 2 years :)
I don't understand. Isn't the init_cache_f_r() which turns on the
cache?
Yes it turns on the cache, but turns off the ROM cache (they are different things). So this ordering is much faster. I think I might have more tuning to do though.
Got it. Since we moved these 3 routines from init_sequence_f_r[] to init_sequence_f[], how about we remove the whole init_sequence_f_r[] completely? If not possible, the comment block above init_sequence_f_r[] needs to be fixed?
I'll remove the comment.
I think init_sequence_f_r can go... but I need to have a better look at the code
If turning off the ROM cache by init_cache_f_r is the problem, then perhaps the following order would be better:
copy_uboot_to_ram, init_cache_f_r, clear_bss, do_elf_reloc_fixups,
Without enabling the CPU's cache, clear_bss and do_elf_reloc_fixups will suffer.
- The '_f_r' sequence must, as a minimum, copy U-Boot to RAM (if
- supported). It _should_, if possible, copy global data to RAM and
- initialise the CPU caches (to speed up the relocation process)
- NOTE: At present only x86 uses this route, but it is intended that
- all archs will move to this when generic relocation is implemented.
*/
So looks that we should either drop this _f_r stage, or make other arch use this _f_r?
I think we should move to generic relocation, meaning that all archs do relocation the same way with the same code. Then only arch-specific stuff is the then ELF fixup function, which adjusts a relocation site, and the code to actually change the stack pointer.
This was always my plan - have arch specific do_reloc_fixups and the rest would be generic
This board_init_f_r() code is part of one attempt to do this - the premise was that turning the cache on before relocating U-Boot will save time. That's true, but it would be even better to turn the cache on much earlier. With pit (Chromebook 2) we turn on the cache in SPL. So I think turning it on here is too late if we are trying to save time. Still it is a good start and if we could make it happen generally it would be nice.
And now you have me thinking board_init_f_r is not needed at all...
If we can setup the stack, clear BSS, copy U-Boot to RAM and perform relocation fixups while running from ROM, what is left for board_init_f_r to do?
The only thing I can think of is the caveats mentioned in the comment ('static' variables are read-only / Global Data (gd->xxx) is read/write). But aren't these true when running from ROM?
Looking at non-x86 arches, relocate_code() looks to do what copy_uboot_to_ram and clear_bss does in x86 land (not sure about do_elf_reloc_fixups - seems to be arch specific as to whether relocate_code() does this or it is done later (hence the CONFIG_NEEDS_MANUAL_RELOC #define?)
See here for my original attempt, which was tied up with generic board. In the end I untied them and we got one but not the other.
http://lists.denx.de/pipermail/u-boot/2012-February/118409.html
Ah, generic relocation... I really wish my life hadn't taken a hard-left turn when it did. We got so close.
From where I'm looking (fresh eyes - I might be missing something big) we
should be able to do the ROM->RAM copy, BSS clearing, and relocation fixups in board_init_f.
When we return from board_init_f it should be a fairly simple matter of: - Copying the contents of the Global Data structure from CAR to RAM (or from RAM to RAM if your on a platform which initialises RAM before U-Boot) - Set the gd pointer (reserved register) to point to the new copy - Figure out where board_init_r is and jump to it
board_init_r should be able to do any remaining cache tweaks. If cache tweaks cannot be done while executing from RAM then they need to be done in board_init_f
I just cannot see the point of board_init_f_r any more
Since then Albert has tidied up ARM start.S a lot which makes this much
easier.
So that's the background. One of these days I might take another look at it if it doesn't get someone's attention.
Oh dear - it looks like I just put my hand up :)
Regards, Simon
Thanks for the background information. I will take a look. Hope we can achieve generic board support as soon as we can.
Regards, Bin
Regards,
Graeme