On Wed, Mar 24, 2021 at 06:59:21PM +0000, Mark Rutland wrote:

On Wed, Mar 24, 2021 at 06:38:18PM +0000, Will Deacon wrote:

quoted

On Fri, Mar 05, 2021 at 06:38:48AM +0900, Hector Martin wrote:

quoted

Apple ARM64 SoCs have a ton of vendor-specific registers we're going to
have to deal with, and those don't really belong in sysreg.h with all
the architectural registers. Make a new home for them, and add some
registers which are useful for early bring-up.

Signed-off-by: Hector Martin <redacted>
---
 MAINTAINERS                           |  1 +
 arch/arm64/include/asm/sysreg_apple.h | 69 +++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 arch/arm64/include/asm/sysreg_apple.h

diff --git a/MAINTAINERS b/MAINTAINERS
index aec14fbd61b8..3a352c687d4b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -1646,6 +1646,7 @@ B:	https://github.com/AsahiLinux/linux/issues
 C:	irc://chat.freenode.net/asahi-dev
 T:	git https://github.com/AsahiLinux/linux.git
 F:	Documentation/devicetree/bindings/arm/apple.yaml
+F:	arch/arm64/include/asm/sysreg_apple.h

(this isn't needed with my suggestion below).

quoted

 ARM/ARTPEC MACHINE SUPPORT
 M:	Jesper Nilsson [off-list ref]

diff --git a/arch/arm64/include/asm/sysreg_apple.h b/arch/arm64/include/asm/sysreg_apple.h
new file mode 100644
index 000000000000..48347a51d564
--- /dev/null
+++ b/arch/arm64/include/asm/sysreg_apple.h

I doubt apple are the only folks doing this, so can we instead have
sysreg-impdef.h please, and then have an Apple section in there for these
registers? That way, we could also have an imp_sys_reg() macro to limit
CRn to 11 or 15, which is the reserved encoding space for these registers.

We'll cc you for any patches touching the Apple parts, as we don't have
the first clue about what's hiding in there.

For existing IMP-DEF sysregs (e.g. the Kryo L2 control registers), we've
put the definitions in the drivers, rather than collating
non-architectural bits under arch/arm64/.

Yeah, but we could include those here as well.

So far we've kept arch/arm64/ largely devoid of IMP-DEF bits, and it
seems a shame to add something with the sole purpose of collating that,
especially given arch code shouldn't need to touch these if FW and
bootloader have done their jobs right.

Can we put the definitions in the relevant drivers? That would sidestep
any pain with MAINTAINERS, too.

If we can genuinely ignore these in arch code, then sure. I just don't know
how long that is going to be the case, and ending up in a situation where
these are scattered randomly throughout the tree sounds horrible to me.

Will