Viable PPC platform?

Viable PPC platform?

[geneSmith]

I have a ppc405gpr system with 64M ram and 4Meg flash in a AM29LV320. Is 
this a viable platform for linux? Can a filesystem (JFFS2?) be put this 
flash type?

-- 
Lit up like Levy's

Re: Viable PPC platform?

[Matt Porter]

On Tue, May 09, 2006 at 10:38:19AM -0400, geneSmith wrote:
> I have a ppc405gpr system with 64M ram and 4Meg flash in a AM29LV320. Is 
> this a viable platform for linux? Can a filesystem (JFFS2?) be put this 
> flash type?

Yes. (Yes) Yes.

-Matt

Re: Viable PPC platform?

[Alex Zeffertt]

On Tue, 09 May 2006 10:38:19 -0400
geneSmith <gd.smth@gmail.com> wrote:

> I have a ppc405gpr system with 64M ram and 4Meg flash in a
> AM29LV320. Is this a viable platform for linux? Can a filesystem
> (JFFS2?) be put this flash type?
> 

I would create an initrd and put every file that doesn't need
to be changed persistently into it instead of JFFS2.

The reason for this is that if JFFS2 becomes too full (less than 5
free blocks) you may find that writes to it hang.

Alex

> -- 
> Lit up like Levy's
> 
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded

Re: Viable PPC platform?

[Eugene Surovegin]

On Tue, May 09, 2006 at 05:41:01PM +0100, Alex Zeffertt wrote:
> On Tue, 09 May 2006 10:38:19 -0400
> geneSmith <gd.smth@gmail.com> wrote:
> 
> > I have a ppc405gpr system with 64M ram and 4Meg flash in a
> > AM29LV320. Is this a viable platform for linux? Can a filesystem
> > (JFFS2?) be put this flash type?
> > 
> 
> I would create an initrd and put every file that doesn't need
> to be changed persistently into it instead of JFFS2.

After many years of doing embedded Linux stuff I still don't 
understand why people are so fond of initrd.

For temporary stuff - tempfs is much better and flexible. For r/o 
stuff - just make separate MTD partition (cramfs, squashfs) and mount 
it directly as root. Both options will waste significantly less 
memory.

-- 
Eugene

Re: Viable PPC platform?

[Wolfgang Denk]

In message <20060509171520.GA10886@gate.ebshome.net> you wrote:
>
> After many years of doing embedded Linux stuff I still don't 
> understand why people are so fond of initrd.
> 
> For temporary stuff - tempfs is much better and flexible. For r/o 
> stuff - just make separate MTD partition (cramfs, squashfs) and mount 
> it directly as root. Both options will waste significantly less 
> memory.

Agreed.

And if somebody wants to see facts and numbers, please see
http://www.denx.de/wiki/view/DULG/RootFileSystemSelection

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Ninety-Ninety Rule of Project Schedules:
        The first ninety percent of the task takes ninety percent of
the time, and the last ten percent takes the other ninety percent.

Re: Viable PPC platform?

[David Woodhouse]

On Wed, 2006-05-10 at 00:31 +0200, Wolfgang Denk wrote:
> And if somebody wants to see facts and numbers, please see
> http://www.denx.de/wiki/view/DULG/RootFileSystemSelection

Out of interest, how old is that JFFS2 test? If it's with the ancient
code in the 2.4 kernel, you'll get a _lot_ of improvement by using the
2.6 kernel.

It looks like it took about 13 seconds to mount the onboard 8MiB flash.
I can mount 512MiB of flash in 7.9 seconds with the current kernel, with
a 400MHz AMD Geode.

There's more work going on right now to reduce the memory usage too.

-- 
dwmw2

Re: Viable PPC platform?

[Wolfgang Denk]

In message <1148334674.10288.30.camel@shinybook.infradead.org> you wrote:
>
> Out of interest, how old is that JFFS2 test? If it's with the ancient
> code in the 2.4 kernel, you'll get a _lot_ of improvement by using the
> 2.6 kernel.

This was on a MPC860 system running a 2.4.25 kernel tree with  a  MTD
snapshot of Spring 2005.

> It looks like it took about 13 seconds to mount the onboard 8MiB flash.
> I can mount 512MiB of flash in 7.9 seconds with the current kernel, with
> a 400MHz AMD Geode.

The file system size was actually only 4 MiB.

But then, a 400 MHz Geode is a bit faster than a 50 MHz 8xx, probably
not only in terms of CPU performance but  also  in  terms  of  memory
bandwidth.

> There's more work going on right now to reduce the memory usage too.

Fine, thanks!

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Make it right before you make it faster.

Re: Viable PPC platform?

[David Woodhouse]

On Tue, 2006-05-23 at 00:15 +0200, Wolfgang Denk wrote:
> But then, a 400 MHz Geode is a bit faster than a 50 MHz 8xx, probably
> not only in terms of CPU performance but  also  in  terms  of  memory
> bandwidth.

It's actually NAND flash, and the bandwidth sucks (the flash controller
on the Geode companion chip is quite slow). We're getting about 3 MiB/s
from it, although we _ought_ to be able to get 3½. I'm playing with
JFFS2 some more before I go back to tweaking the NAND drivers though.

-- 
dwmw2

Re: Viable PPC platform?

[Alex Zeffertt]

On Tue, 9 May 2006 10:15:20 -0700
Eugene Surovegin <ebs@ebshome.net> wrote:

> On Tue, May 09, 2006 at 05:41:01PM +0100, Alex Zeffertt wrote:
> > On Tue, 09 May 2006 10:38:19 -0400
> > geneSmith <gd.smth@gmail.com> wrote:
> > 
> > > I have a ppc405gpr system with 64M ram and 4Meg flash in a
> > > AM29LV320. Is this a viable platform for linux? Can a filesystem
> > > (JFFS2?) be put this flash type?
> > > 
> > 
> > I would create an initrd and put every file that doesn't need
> > to be changed persistently into it instead of JFFS2.
> 
> After many years of doing embedded Linux stuff I still don't 
> understand why people are so fond of initrd.
> 
> For temporary stuff - tempfs is much better and flexible. For r/o 
> stuff - just make separate MTD partition (cramfs, squashfs) and
> mount it directly as root. Both options will waste significantly
> less memory.
> 

Okay, let me qualify my answer.  It depends on whether you need to
make persistent changes to the filesystem in flash.  If so, and given
that your flash is only 4MB, I would recommend moving files to
somewhere else, e.g. an initrd, because if when a JFFS2 FS is
approaching full, you often find that writes to flash hang
while JFFS2 searches for blocks to use as a scratchpad.  This has been
my experience anyway.

If you don't need to make persistent changes to files, then I'm sure
cramfs in flash as a rootfs would work well, with a tmpfs partition
mounted on /tmp and /var.

Alex

Re: Viable PPC platform?

[Eugene Surovegin]

On Wed, May 10, 2006 at 12:11:41PM +0100, Alex Zeffertt wrote:
> On Tue, 9 May 2006 10:15:20 -0700
> Eugene Surovegin <ebs@ebshome.net> wrote:
> 
> > On Tue, May 09, 2006 at 05:41:01PM +0100, Alex Zeffertt wrote:
> > > On Tue, 09 May 2006 10:38:19 -0400
> > > geneSmith <gd.smth@gmail.com> wrote:
> > > 
> > > > I have a ppc405gpr system with 64M ram and 4Meg flash in a
> > > > AM29LV320. Is this a viable platform for linux? Can a filesystem
> > > > (JFFS2?) be put this flash type?
> > > > 
> > > 
> > > I would create an initrd and put every file that doesn't need
> > > to be changed persistently into it instead of JFFS2.
> > 
> > After many years of doing embedded Linux stuff I still don't 
> > understand why people are so fond of initrd.
> > 
> > For temporary stuff - tempfs is much better and flexible. For r/o 
> > stuff - just make separate MTD partition (cramfs, squashfs) and
> > mount it directly as root. Both options will waste significantly
> > less memory.
> > 
> 
> Okay, let me qualify my answer.  It depends on whether you need to
> make persistent changes to the filesystem in flash.  If so, and given
> that your flash is only 4MB, I would recommend moving files to
> somewhere else, e.g. an initrd, because if when a JFFS2 FS is
> approaching full, you often find that writes to flash hang
> while JFFS2 searches for blocks to use as a scratchpad.  This has been
> my experience anyway.
> 
> If you don't need to make persistent changes to files, then I'm sure
> cramfs in flash as a rootfs would work well, with a tmpfs partition
> mounted on /tmp and /var.

You missed my point. initrd should be stored somewhere - in the same 
flash . In this case there is no reason to actually use initrd instead 
of just direct mount from flash.

-- 
Eugene

RE: Viable PPC platform?

[Howard, Marc]

> -----Original Message-----
> From:=20
> linuxppc-embedded-bounces+marc.howard=3Dkla-tencor.com@ozlabs.or
g [mailto:linuxppc-embedded-bounces+marc.howard=3Dkla->
tencor.com@ozlabs.org] On Behalf Of Wolfgang Denk
> Sent: Tuesday, May 09, 2006 3:31 PM
> To: Eugene Surovegin
> Cc: linuxppc-embedded@ozlabs.org
> Subject: Re: Viable PPC platform?=20
>=20
> In message <20060509171520.GA10886@gate.ebshome.net> you wrote:
> >
> > After many years of doing embedded Linux stuff I still don't=20
> > understand why people are so fond of initrd.
> >=20
> > For temporary stuff - tempfs is much better and flexible. For r/o=20
> > stuff - just make separate MTD partition (cramfs, squashfs)=20
> and mount=20
> > it directly as root. Both options will waste significantly less=20
> > memory.
>=20
> Agreed.
>=20
> And if somebody wants to see facts and numbers, please see
> http://www.denx.de/wiki/view/DULG/RootFileSystemSelection
>=20

One size does not fit all.  We have an application with a very large
file system.  It can't fit in the available flash, however we do have a
ton of RAM (512MB).  NFS is not an option nor is it desirable (latency
and availability issues).  Boot time is not an issue either in this case
as it takes the equipment many minutes to calibrate and initialize.

initrd also solves another problem.  The combined uBoot multi-image
although huge (>32 MB) represents a complete system firmware snapshot in
a single (huge) file.  By selecting the appropriate uImage the host can
guarantee the linux build, device drivers, application version and FPGA
firmware revs (the embedded board is rebooted to guarantee a repeatable
starting state).  This makes revision control for the overall system
much easier, especially since the host system is running windoze.

I agree with your general conclusion but there are specific cases where
it is not optimal.

Marc W. Howard

Re: Viable PPC platform?

[Eugene Surovegin]

On Tue, May 09, 2006 at 03:52:20PM -0700, Howard, Marc wrote:
> > 
> > In message <20060509171520.GA10886@gate.ebshome.net> you wrote:
> > >
> > > After many years of doing embedded Linux stuff I still don't 
> > > understand why people are so fond of initrd.
> > > 
> > > For temporary stuff - tempfs is much better and flexible. For r/o 
> > > stuff - just make separate MTD partition (cramfs, squashfs) 
> > and mount 
> > > it directly as root. Both options will waste significantly less 
> > > memory.
> > 
> > Agreed.
> > 
> > And if somebody wants to see facts and numbers, please see
> > http://www.denx.de/wiki/view/DULG/RootFileSystemSelection
> > 
> 
> One size does not fit all.  We have an application with a very large
> file system.  It can't fit in the available flash, however we do have a
> ton of RAM (512MB).  NFS is not an option nor is it desirable (latency
> and availability issues).  Boot time is not an issue either in this case
> as it takes the equipment many minutes to calibrate and initialize.
> 
> initrd also solves another problem.  The combined uBoot multi-image
> although huge (>32 MB) represents a complete system firmware snapshot in
> a single (huge) file.  By selecting the appropriate uImage the host can
> guarantee the linux build, device drivers, application version and FPGA
> firmware revs (the embedded board is rebooted to guarantee a repeatable
> starting state).  This makes revision control for the overall system
> much easier, especially since the host system is running windoze.

This all is nice provided you use network for boot. IMHO this is quite 
_rare_ setup (especially Windows host!!!). For 99% of embedded designs 
this is obviously not a viable option.

-- 
Eugene

RE: Viable PPC platform?

[Howard, Marc]

 > -----Original Message-----
> From: Eugene Surovegin [mailto:ebs@ebshome.net]=20

> > > In message <20060509171520.GA10886@gate.ebshome.net> you wrote:
> > > >
> > > > After many years of doing embedded Linux stuff I still don't=20
> > > > understand why people are so fond of initrd.
> > > >=20
> > One size does not fit all.  We have an application with a very large
> > file system.  It can't fit in the available flash, however=20
> we do have a
> > ton of RAM (512MB).  NFS is not an option nor is it=20
> desirable (latency
> > and availability issues).  Boot time is not an issue either=20
> in this case
> > as it takes the equipment many minutes to calibrate and initialize.
> >=20
> > initrd also solves another problem.  The combined uBoot multi-image
> > although huge (>32 MB) represents a complete system=20
> firmware snapshot in
> > a single (huge) file.  By selecting the appropriate uImage=20
> the host can
> > guarantee the linux build, device drivers, application=20
> version and FPGA
> > firmware revs (the embedded board is rebooted to guarantee=20
> a repeatable
> > starting state).  This makes revision control for the overall system
> > much easier, especially since the host system is running windoze.
>=20
> This all is nice provided you use network for boot. IMHO this=20
> is quite=20
> _rare_ setup (especially Windows host!!!). For 99% of=20
> embedded designs=20
> this is obviously not a viable option.
>=20
> --=20
> Eugene

Again, I agree.  I just wanted to show you at least one case where
initrd is the best solution, IMHO.

As for a linux board booting off of a windoze host I prefer to think of
it as an island of sanity in a sea of chaos.

Marc W. Howard