On 14-06-10 01:35 PM, Wolfgang Denk wrote:
Dear Steve,
In message <53975ec2.1080...@broadcom.com> you wrote:
I still cannot understand why _start and CONFIG_SYS_TEXT_BASE would
have to be the same. There is no such requirement. What exactly
prevents you from assigning _start a location at offset 0x20 to the
start of the text segment, i. e. CONFIG_SYS_TEXT_BASE ?
Wolfgang et al.
I agree that they do not need to be the same...
So our issue is that basically "for every ARMv7 board in the company",
we are currently maintaining our own modified/customized version of
"arch/arm/cpu/armv7/start.S" in order to add the appropriate 32 byte
header...
There should be more clever ways to implement this. If nothing else
comes to mind, an #ifdef in "arch/arm/cpu/armv7/start.S" should be
sufficient to condistionally insert / adjust any offset that might be
needed for a specific board.
And we could choose to do it using other methods, but they all require
us to maintain a customized version of linker scripts, or some other
code, or ....
... or a CONFIG setting in your board config file resp. your board's
defconfig.
The request here is that with the addition of some relatively
straightforward (upstreamed) code, then this can be handled
automatically by a post-processing step and we would be able to use a
pristine version of the upstreamed code...
I'm sorry, but I disagree especially on the "straightforward" part.
Also, I see no reason to make the existing code unnecessarily complex,
and add more disadvantages (like increased meory footprint etc.) when
the same purpose can be implemented without adding any special code at
all.
Our desire is to get this into the beginnings of the "ARMv8" boards, so
that we can avoid the maintenance issues we have with the current ARMv7
boards.
We appreciate your consideration of this request.
These are two different things: implementing a clean and easy way to
support a necessary feature is one thing; to do it in the suggested
way by adding code where none is needed is another thing.
I'm all for adding support for any features that are useful, even if
only for a single user, as long as they don't hurt other users. All
I'm asking is to chose another way to implement this feature. So far,
I did not see any arguments that my alternative proposals would cause
any problems to you?
OK - I think that one of the alternate proposals would be to
conditionally reserve a "32 byte block" prior to the _start symbol (in
"arch/arm/cpu/armv8/start.S") which would then be filled in by a
post-processing step... This could be implemented by:
diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index 4b11aa4..8fd72f1 100644
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -18,6 +18,10 @@
*
*************************************************************************/
+#ifdef CONFIG_CUSTOM_HEADER_RESERVED_BYTES
+ .skip CONFIG_CUSTOM_HEADER_RESERVED_BYTES
+#endif
+
.globl _start
_start:
b reset
And then in our board config file:
#define CONFIG_CUSTOM_HEADER_RESERVED_BYTES 32
And we could implement a similar algorithm in the armv7/start.S as you
stated above.
Are we understanding your proposals properly? Would this be an
acceptable solution?
Thanks, Steve
Best regards,
Wolfgang Denk
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