Add Beaglebone Black support to GENERIC
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Authored by andrew on Oct 25 2016, 6:35 PM.

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Reviewers

imp
mmel

Group Reviewers

ARM

Commits

rS308214: Add BeagleBone Black support to GENERIC on armv6.
rS308213: Allow an SMP kernel to boot on Cortex-A8:

Summary

Allow the Cortex-A8 to boot a SMP kernel by only setting PRRR_NS1 when we have MP extensions.
Only use ARM_HAVE_MP_EXTENSIONS to determine if we should use the IS register variants.
Add the Ti bits from the BEAGLEBONE config to GENERIC

Test Plan

I've only booted on a Beaglebone Black.
Someone should check if GENERIC still boots on existing hardware supported
by GENERIC.

Diff Detail

Repository

rS FreeBSD src repository - subversion

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No Test Coverage

Build Status

Buildable 5810
Build 6102: arc lint + arc unit

Event Timeline

andrew updated this revision to Diff 21677.Oct 25 2016, 6:35 PM

andrew retitled this revision from to Add Beaglebone Black support to GENERIC.

andrew updated this object.

andrew edited the test plan for this revision. (Show Details)

andrew added a reviewer: ARM.

Herald added a subscriber: imp. · View Herald TranscriptOct 25 2016, 6:35 PM

Just successfully booted my olimex a20-som-evb with this patch.

looks reasonable to me, haven't tested it on my BBB though.

This revision is now accepted and ready to land.Oct 25 2016, 11:09 PM

Removal of "defined SMP" from "#if __ARM_ARCH >= 7 && defined SMP" is bogus. GENERIC kernel must have SMP defined, right? All those macros are unusable on UP kernels and proper #if's works as simple but valuable safe keeper.

This revision now requires changes to proceed.Oct 26 2016, 3:51 AM

In D8335#173687, @meloun-miracle-cz wrote:

Removal of "defined SMP" from "#if __ARM_ARCH >= 7 && defined SMP" is bogus. GENERIC kernel must have SMP defined, right?

Why?

All those macros are unusable on UP kernels and proper #if's works as simple but valuable safe keeper.

No, the macros are unable to be executed on Cortex-A8. This doesn't mean they are unable to be included in a kernel, just that we shouldn't execute them.

There are cases where we may need them in a UP kernel. From on of your comments in D8092:

"I have system where first CPU core is used for FreeBSD, second one is dedicated for application computing (without kernel), but SMP coherency I still required."

This should work with a UP kernel as FreeBSD is only running on a single core, however this is impossible with the current code.

In D8335#173769, @andrew wrote:

In D8335#173687, @meloun-miracle-cz wrote:

Removal of "defined SMP" from "#if __ARM_ARCH >= 7 && defined SMP" is bogus. GENERIC kernel must have SMP defined, right?

Why?

Because nobody (i hope) want to start using slower (broadcasted) version of TLB operation for UP kernel..

All those macros are unusable on UP kernels and proper #if's works as simple but valuable safe keeper.

No, the macros are unable to be executed on Cortex-A8. This doesn't mean they are unable to be included in a kernel, just that we shouldn't execute them.

That's not a true. MP extensions are mandatory only for A15. All other may exist without it. And there are single core SOCs (to be fair, I have no idea if these have MP implemented or not).

There are cases where we may need them in a UP kernel. From on of your comments in D8092:

"I have system where first CPU core is used for FreeBSD, second one is dedicated for application computing (without kernel), but SMP coherency I still required."

This should work with a UP kernel as FreeBSD is only running on a single core, however this is impossible with the current code.

No, my comment was about SMP kernel running on single core, not about UP kernel. So (currently) all works as expected.

With current code, we can run UP kernel on dual core CPU without disturbing other core by TLB (or cache) broadcasts in non-coherent mode, or we can run SMP kernel on single core while other CPU is SMP coherent.
I don't want to break this model.

For me, right case is to have compiled non-broadcasted version for UP kernel, broadcasted version for SMP kernel and runtime selected version for GENERIC kernel only.