ARMKernelVersionAlignment

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Revision 3 as of 2010-05-18 13:46:48
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Editor: 5ac884b8
Comment: Add notes from UDS-M session
Revision 4 as of 2010-05-31 04:13:46
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Editor: npitre
Comment:
Deletions are marked like this. Additions are marked like this.
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 * '''Created''':
 * '''Contributors''':
 * '''Packages affected''':
 * '''Created''': NicolasPitre
 * '''Contributors''': NicolasPitre
 * '''Packages affected''': kernel
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This should provide an overview of the issue/functionality/change proposed here. Focus here on what will actually be DONE, summarising that so that other people don't have to read the whole spec. See also CategorySpec for examples. Establish a process and work flow to integrate together constantly evolving
kernel source trees from various independent sources in order to merge the
result into the main Ubuntu kernel source package in a controlled way.
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This section should include a paragraph describing the end-user impact of this change. It is meant to be included in the release notes of the first release in which it is implemented. (Not all of these will actually be included in the release notes, at the release manager's discretion; but writing them is a useful exercise.)

It is mandatory.
Ubuntu 10.10 is made of a common kernel source tree across all supported
architectures and target, including ARM.
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This should cover the _why_: why is this change being proposed, what justifies it, where we see this justified. Unlike for X86, what we generally refer to when mentioning "ARM"
is pretty eclectic. While ARM Ltd has defined and standardized the ARM
instruction set, the ARM licensees (i.e. those who actually produce chips)
have integrated that technology into wildly different SOCs. Therefore,
there isn't such thing as a "common ARM architecture" as we mean it when
talking about the "X86 architecture".

Those different ARM vendors have used their own set of IP blocks around the ARM
CPU core, such as timers, interrupt controllers, memory controllers, IO
peripherals, etc. Even the MMU architecture has seen some variations
between different vendors and different revisions of the ARM architecture.

There is some on-going work at ARM Ltd to standardize more pieces of an ARM
system into a common specification. But the ARM systems we have to deal
with today come from different vendors, and they should be considered almost
like different architectures when it comes to software support. This is
also why those vendors usually provide their own set of patches for their
product.

The problem of course is a diverse set of large patch series for separate SOC
families, based on different kernel versions, and with different "quality of
implementation". Those different SOC families have their own on-going
development and particular issues.

Until now, Ubuntu on ARM has used different kernel source packages, sometimes
even using different base kernel versions, to cope with the kernel
discrepencies between all supported vendors. But this is causing no end of
support, maintenance and QA issues.

Summary

Establish a process and work flow to integrate together constantly evolving kernel source trees from various independent sources in order to merge the result into the main Ubuntu kernel source package in a controlled way.

Release Note

Ubuntu 10.10 is made of a common kernel source tree across all supported architectures and target, including ARM.

Rationale

Unlike for X86, what we generally refer to when mentioning "ARM" is pretty eclectic. While ARM Ltd has defined and standardized the ARM instruction set, the ARM licensees (i.e. those who actually produce chips) have integrated that technology into wildly different SOCs. Therefore, there isn't such thing as a "common ARM architecture" as we mean it when talking about the "X86 architecture".

Those different ARM vendors have used their own set of IP blocks around the ARM CPU core, such as timers, interrupt controllers, memory controllers, IO peripherals, etc. Even the MMU architecture has seen some variations between different vendors and different revisions of the ARM architecture.

There is some on-going work at ARM Ltd to standardize more pieces of an ARM system into a common specification. But the ARM systems we have to deal with today come from different vendors, and they should be considered almost like different architectures when it comes to software support. This is also why those vendors usually provide their own set of patches for their product.

The problem of course is a diverse set of large patch series for separate SOC families, based on different kernel versions, and with different "quality of implementation". Those different SOC families have their own on-going development and particular issues.

Until now, Ubuntu on ARM has used different kernel source packages, sometimes even using different base kernel versions, to cope with the kernel discrepencies between all supported vendors. But this is causing no end of support, maintenance and QA issues.

User stories

Assumptions

Design

You can have subsections that better describe specific parts of the issue.

Implementation

This section should describe a plan of action (the "how") to implement the changes discussed. Could include subsections like:

UI Changes

Should cover changes required to the UI, or specific UI that is required to implement this

Code Changes

Code changes should include an overview of what needs to change, and in some cases even the specific details.

Migration

Include:

  • data migration, if any
  • redirects from old URLs to new ones, if any
  • how users will be pointed to the new way of doing things, if necessary.

Test/Demo Plan

It's important that we are able to test new features, and demonstrate them to users. Use this section to describe a short plan that anybody can follow that demonstrates the feature is working. This can then be used during testing, and to show off after release. Please add an entry to http://testcases.qa.ubuntu.com/Coverage/NewFeatures for tracking test coverage.

This need not be added or completed until the specification is nearing beta.

Unresolved issues

This should highlight any issues that should be addressed in further specifications, and not problems with the specification itself; since any specification with problems cannot be approved.

BoF agenda and discussion

Kernel Version

With the current upstream cadence we are expecting v2.6.35 to release mid to late september. With a likely Maverick kernel freeze date at the end of September, we are therefore unable to take an early v2.6.36 release.

The decision therefore is v2.6.35 for Maverick.

ARM VERSIONS

Need to try and get the vendors on the same level, at v2.6.35.

For OMAP3 we are expecting to have a small delta, and hope to get that as a merged branch (in master) and use that as reference platform.

OMAP4 support in 2.6.35 will be there, but very basic, not enough for a full ubuntu stack. There is a fair pile of patches pending for upstream. Likely we will have an OMAP4 enablement branch to allow the full stack to be applied. It will beed backports from v2.6.36.

Most of the ARM bugfixes fixes are already scheduled for v2.6.35, there are some features coming but not significant for us.

Freescale: they are currently planning on v2.6.34. they have timing constraints due to new silicon appearing around v2.6.35 release date

Marvell: v2.6.32, mostly upstream from v2.6.34. It is therefore possible v2.6.35 will just work for Dove. Still may be some patches needed for more than 'basic' support; display is missing.

Samsung: currently targetting v2.6.34 and have some 60 patches on top.

Smoothstone: missing the v2.6.35 window, a fairly large patch stack

Get the message out that we want to get proposed patches for ARM merging around v2.6.35-rc2


CategorySpec

Specs/M/ARMKernelVersionAlignment (last edited 2010-08-27 05:14:15 by npitre)