xtensa: support configurable processor configurations

Xtensa is a configurable processor architecture, which allows to define additional instructions and registers. The required variant specific information for the toolchain is delivered in an 'overlay' file, which needs to be 'untarred' to the corresponding directories after the source is installed and patched.
This patch provides support for binutils, gcc, and gdb with a very limited changes to the build scripts. These additions are only executed for the Xtensa architecture and have no effect on other architectures.

Signed-off-by Chris Zankel<[email protected]>

arch/Config.in.xtensa new file +0 -0

new file mode 100644
index 0000000..61c0235

arch/Config.in.xtensa line 9

Quoted 5 lines · Chris Zankel

arch/Config.in.xtensa new file +5 -0

+config BR2_xtensa_custom
+	bool "Custom Xtensa processor configuration"
+config BR2_xtensa_fsf
+	bool "fsf - Default configuration"
+endchoice

Put empty lines between the different config options.

All config names should be in capitals - the only exception is the
arch name itself (i.e. BR2_xtensa, but BR2_XTENSA_FSF).

arch/Config.in.xtensa line 12

Quoted 3 lines

arch/Config.in.xtensa new file +3 -0

+
+config BR2_xtensa_custom_name
+	string "Custom Xtensa processor configuration anme"

anme -> name

arch/Config.in.xtensa line 21

Quoted 10 lines

arch/Config.in.xtensa new file +9 -0

+	depends on BR2_xtensa_custom
+	default ""
+	help
+	  Name given to a custom Xtensa processor configuration.
+
+config BR2_xtensa_core_name
+	string
+	default BR2_xtensa_custom_name	if BR2_xtensa_custom
+	default ""			if BR2_xtensa_fsf

Minor detail: missing "depends on BR2_xtensa".

Perhaps it's better to move the condition to a
if BR2_xtensa
...
endif
around the entire file. Thomas has a patch lined up to move all the conditions outside of the Config.in.*

arch/Config.in.xtensa line 30

Quoted 9 lines

arch/Config.in.xtensa new file +9 -0

+
+config BR2_xtensa_overlay_dir
+	string "Overlay directory for custom configuration"
+	depends on BR2_xtensa_custom
+	default ""
+	help
+	  Provide a directory path that contains the overlay files
+	  for the custom configuration. The path is based on the
+	  buildroot top directory.

based on -> relative to

I don't find this explanation sufficient. First of all, it should
mention that that directory should contain tar files. Second, it would help if you could explain where the tar files are supposed to come from (I guess they're generated by some Xtensa tool).

Hi Arnout,

Quoted 7 lines · Arnout Vandecappelle

arch/Config.in.xtensa line 9

Quoted 5 lines · Chris Zankel

arch/Config.in.xtensa new file +5 -0

+config BR2_xtensa_custom
+	bool "Custom Xtensa processor configuration"
+config BR2_xtensa_fsf
+	bool "fsf - Default configuration"
+endchoice

Put empty lines between the different config options.

Done.

Quoted 2 lines

All config names should be in capitals - the only exception is the
arch name itself (i.e. BR2_xtensa, but BR2_XTENSA_FSF).

To give you some background, 'fsf' describes the default configuration used in the various toolchain packages (gcc, buildroot, etc.). The idea is to append the name of the processor configuration (for example, dc232b), so to follow other architectures, I think it would be best to keep lower-case for processor names, and upper case for other options.

For the case above, it would look like this:

config BR_XTENSA_CUSTOM
...

config BR_xtensa_fsf
...

config BR_xtensa_dc232b
...

etc.

I actually think that this makes a nice distinction between processor names and buildroot configuration options.

Quoted 6 lines

arch/Config.in.xtensa line 12

Quoted 5 lines

arch/Config.in.xtensa new file +3 -0

+
+config BR2_xtensa_custom_name
+	string "Custom Xtensa processor configuration anme"

anme -> name

Done

Quoted 11 lines

arch/Config.in.xtensa line 21

Quoted 10 lines

arch/Config.in.xtensa new file +9 -0

+	depends on BR2_xtensa_custom
+	default ""
+	help
+	  Name given to a custom Xtensa processor configuration.
+
+config BR2_xtensa_core_name
+	string
+	default BR2_xtensa_custom_name	if BR2_xtensa_custom
+	default ""			if BR2_xtensa_fsf

Minor detail: missing "depends on BR2_xtensa".

Done.

Quoted 6 lines

Perhaps it's better to move the condition to a
if BR2_xtensa
...
endif
around the entire file. Thomas has a patch lined up to move all the conditions outside of the Config.in.*

It seems Xtensa would be the only one that uses that scheme, so maybe wait for the generic patch from Thomas?

Perhaps it's better to move the condition to a
if BR2_xtensa
...
endif
around the entire file. Thomas has a patch lined up to move all the conditions outside of the Config.in.*

Quoted 2 lines

It seems Xtensa would be the only one that uses that scheme, so maybe wait for the generic patch from Thomas?

I don't think so. Then it means more work for Thomas to refresh his
patch. There will be a merge conflict anyway between the two, but with the condition outside the file the conflict will be small.

That said, Peter hasn't merged Thomas's patch even though I acked
it, so maybe he has some fundamental objection to the principle. Or maybe it's just because I didn't test it.

Quoted 13 lines · Arnout Vandecappelle

Perhaps it's better to move the condition to a
if BR2_xtensa
...
endif
around the entire file. Thomas has a patch lined up to move all the conditions outside of the Config.in.*

Quoted 2 lines

It seems Xtensa would be the only one that uses that scheme, so maybe wait for the generic patch from Thomas?

I don't think so. Then it means more work for Thomas to refresh his
patch. There will be a merge conflict anyway between the two, but with the condition outside the file the conflict will be small.

Quoted 3 lines

That said, Peter hasn't merged Thomas's patch even though I acked
it, so maybe he has some fundamental objection to the principle. Or maybe it's just because I didn't test it.

I guess I don't understand what that patch does, i.e. where is the 'if...endif'? Could you maybe point to the patch?

Quoted 2 lines

I guess I don't understand what that patch does, i.e. where is the 'if...endif'? Could you maybe point to the patch?

I'm talking about http://patchwork.ozlabs.org/patch/196916/
In arch/Config.in, it introduces the following construct:

if BR2_xtensa
source "arch/Config.in.xtensa"
endif

This removes the need for adding 'depend on BR2_xtensa' in every config
option in that file.

It's true that _now_ xtensa would be the only one using that scheme, but the
idea is that if you do that for xtensa now, it will be easier to merge in Thomas's patch later (or vice versa, it will be easier to rebase your patch once Thomas's patch gets merged).

Sorry, I got your email after I sent out version 4 of the patch, which doesn't include the change you mentioned (somehow, fetchmail was stuck :-( So, please let me know if you want me to send out another version that includes that change. I don't want to confuse Thomas with all those versions...

Chris,

Quoted 5 lines · Chris Zankel

Sorry, I got your email after I sent out version 4 of the patch, which doesn't include the change you mentioned (somehow, fetchmail was stuck :-( So, please let me know if you want me to send out another version that includes that change. I don't want to confuse Thomas with all those versions...

You can keep your patch as is wrt to Config.in. What I propose to do is that I merge your Xtensa support in one of my branch together with my reorganization of the architecture definitions and I send a pull-request for the whole thing to Peter.

Would that be OK for you?