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[ts-7000] Re: TS7200/7250 Linux kernel

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Subject: [ts-7000] Re: TS7200/7250 Linux kernel
From: "Jesse Off" <>
Date: Tue, 25 Oct 2005 19:36:30 -0000
--- In  "Wagner Scott (ST-IN/ENG1)"
<> wrote:
>
> Hi all,
> 
> The issue of a 2.6 kernel for the TS7200 has once again been raised.  In
> my opinion, the path to a useful 2.6 kernel is dependent upon a
> well-understood kernel patch chain to generate the existing 2.4 TS7250
> kernel.

I honestly don't understand the fixation with a 2.6 kernel, especially
since there is no official ep93xx support in 2.6 either so its not
like its better supported by Linus and crew.  TS does not have the
resources to support 2 separate versions of Linux kernels.  Despite
the presumption of this thread, there is surprisingly few customers
demanding 2.6-- when it comes down to it, there just really isn't much
difference between 2.4 vs 2.6 unless you delve into minutae such as
details of the thread scheduler that don't apply to 99.99% of people
designing embedded products.  What we've found instead is an emotional
desire from the hard-core Linux advocates to be "bleeding-edge"
without sufficient justifiable rational reasoning.

Seriously though, TS just hasn't been 'sold' enough on the 2.6 sales
pitch yet to commit to tabling our current endeavors to work on 2.6
instead.  We are a very old-school set of engineers that have been
well served with the saying "if it ain't broke, don't fix it" and
nothing seems obviously broken with 2.4.  This, of course, can change
if 1) we have a large customer legitimately require and/or fund 2.6
development or 2) we can be shown real-life advantages of 2.6 that
outweigh the costs and risks.  (Big-Oh notation algorithm
improvements, 200% performance improvements for 1% of apps, driver
updates that can only be described as "better...", or other marketing
dribble are not likely to impress)  

> 
> TS documentation indicates that the TS kernel is patched against a
> Cirrus EP93xx kernel, which is in turn patched against kernel.org
> sources.

Its actually worse than that.  Its Linux 2.4.26 vanilla, plus some ARM
specific patchset by the name of "vrs1", then Cirrus' patches, then
our modifications.  I think the original cirrus-1-2-1 patch was
applied to a linux 2.4.21 kernel, but a previous engineer that is no
longer with TS was able to apply the patch to a Linux 2.4.26 + vrs1. 
I'm not sure I remember why he wanted to diverge from Cirrus default,
but I'm sure it had to do with 2.4.26 being the 2.4 kernel in fashion
at the time.  

> 
> The production TS7250 kernel, labeled 2.4.26-vrs1-cirrus-1-2-1-ts8, is
> claimed to derive from a Cirrus 2.4.26 kernel.  However, I have not
> found a 2.4.26 kernel from Cirrus, and when I ask Cirrus about a 2.4.26
> kernel they are puzzled.  (Cirrus does publish 2.4.18, 2.4.19, and
> 2.4.21 kernels for the EP93xx.)  Thus, I have been unable to reconstruct
> the first link in the patch chain - the patch from kernel.org 2.4.26
> source to a Cirrus EP93xx 2.4.26 kernel.  Furthermore, when I requested
> TS patch sources to the Cirrus kernel, TS suggested that I generate the
> patches from a diff of the TS published source against the (nonexistent)
> Cirrus EP93xx 2.4.26 kernel.  In other words, I'm stuck here.

We've actually diverged enough we probably could just as well call
"-vrs1-cirrus-1-2-1-ts8" only "-ts8".  Even though its GPL, I think
Cirrus still requires you to have an eval board to download their
patches so a patch against a Cirrus kernel is useful only to those
with Cirrus eval boards.  If there exists a booting (from RedBoot) 2.6
kernel for the EDB9302 Cirrus eval board, I'd actually suggest you
start with that rather than trying to work backward from the TS 2.4
source tree.  I highly doubt any of our changes to a 2.4 kernel could
apply in a patch form to the radically different 2.6 kernel.

//Jesse Off









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