Inconsistent accesses to SDRAM on a PCI card

Inconsistent accesses to SDRAM on a PCI card

[Amit Shah]

Hi all,

Since there seems to be no list dedicated to Linux + PCI, I'll ask my
question here.

I have a custom board that has the Marvell 64360 bridge. It has a powerpc
750GX processor on it and 256MB of SDRAM.

I wrote a host driver that could access the RAM via a /dev interface (I'm
using kernel 2.6.6 on the host). I can read / write from the device to the
sdram on the board. I also have u-boot running on the board, so I can
read / write from / to SDRAM on the board via u-boot. Basically, I can dump
a Linux kernel to the board via the host PCI interface and jump to the
kernel on the board via u-boot.

This worked fine while I worked with this setup on an IBM pserver machine.
However, when I switched to a locally assembled machine based on the intel 
SE7210TP1-E [1] chipset, u-boot's and PCI's view of SDRAM on the board
changed completely.

If I dump the kernel to an offset of 5 MB on the board via the PCI
interface, u-boot doesn't see it. The contents before and after dumping the
kernel remain the same. Ditto over the PCI interface. If I do any writes
via u-boot to the SDRAM, the PCI can't see the newly written contents.

This is very strange, I couldn't find an answer anywhere in the BIOS
settings or any kernel settings. Since the kernel, u-boot, host tools, etc,
haven't changed, and it's just the machine that has changed, I'm guessing
it's the PCI interface or the BIOS initializations that are causing some
funny things to happen.

Any clue why this should be happening?

Thanks,
Amit.


[1] http://www.intel.com/design/servers/boards/SE7210TP1-E/

-- 
Amit Shah
http://amitshah.nav.to/



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Re: Inconsistent accesses to SDRAM on a PCI card

[Greg KH]

On Thu, Aug 26, 2004 at 09:48:53PM +0530, Amit Shah wrote:
> Hi all,
> 
> Since there seems to be no list dedicated to Linux + PCI, I'll ask my
> question here.

There is a linux-pci mailing list :)

Or ask this on linux-kernel.

good luck,

greg k-h


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Re: Inconsistent accesses to SDRAM on a PCI card

[Amit Shah]

On Thu, 26 Aug 2004 09:48:33 -0700, Greg KH <greg@kroah.com> wrote:
> On Thu, Aug 26, 2004 at 09:48:53PM +0530, Amit Shah wrote:
> > Hi all,
> >
> > Since there seems to be no list dedicated to Linux + PCI, I'll ask my
> > question here.
> 
> There is a linux-pci mailing list :)

Heh, yeah.

> 
> Or ask this on linux-kernel.

Yup. I thought you'd be the best person to answer it, though...

> good luck,
> 
> greg k-h
-- 
Amit Shah
http://amitshah.nav.to/


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RE: Inconsistent accesses to SDRAM on a PCI card

[Sabharwal, Atul]

Why don't you try to write & readback from memory at 1M intervals
starting
From 1M address.  This way you would be able to determine the memory map
And the range where your SDRAM is mapped.  

My guess is that your problem is that the memory is not mapped at all.
Some
Memory chip vs chipset compatibility issue.  I have heard of problems 
With uboot where the memory controller does not initialize correctly.
They had to change the memory chip to workaround the problem ( increased
$20 cost though).

--
Atul

-------------------------------------------------------------
P.S:  All opinions are my personal opinion(s) & responsibility and do
not represent the view of my employer ( Intel Corporation ).
 

>-----Original Message-----
>From: linux-hotplug-devel-admin@lists.sourceforge.net 
>[mailto:linux-hotplug-devel-admin@lists.sourceforge.net] On 
>Behalf Of Amit Shah
>Sent: Thursday, August 26, 2004 9:19 AM
>To: linux-hotplug-devel@lists.sourceforge.net
>Subject: Inconsistent accesses to SDRAM on a PCI card
>
>Hi all,
>
>Since there seems to be no list dedicated to Linux + PCI, I'll ask my
>question here.
>
>I have a custom board that has the Marvell 64360 bridge. It 
>has a powerpc
>750GX processor on it and 256MB of SDRAM.
>
>I wrote a host driver that could access the RAM via a /dev 
>interface (I'm
>using kernel 2.6.6 on the host). I can read / write from the 
>device to the
>sdram on the board. I also have u-boot running on the board, so I can
>read / write from / to SDRAM on the board via u-boot. 
>Basically, I can dump
>a Linux kernel to the board via the host PCI interface and jump to the
>kernel on the board via u-boot.
>
>This worked fine while I worked with this setup on an IBM 
>pserver machine.
>However, when I switched to a locally assembled machine based 
>on the intel 
>SE7210TP1-E [1] chipset, u-boot's and PCI's view of SDRAM on the board
>changed completely.
>
>If I dump the kernel to an offset of 5 MB on the board via the PCI
>interface, u-boot doesn't see it. The contents before and 
>after dumping the
>kernel remain the same. Ditto over the PCI interface. If I do 
>any writes
>via u-boot to the SDRAM, the PCI can't see the newly written contents.
>
>This is very strange, I couldn't find an answer anywhere in the BIOS
>settings or any kernel settings. Since the kernel, u-boot, 
>host tools, etc,
>haven't changed, and it's just the machine that has changed, 
>I'm guessing
>it's the PCI interface or the BIOS initializations that are 
>causing some
>funny things to happen.
>
>Any clue why this should be happening?
>
>Thanks,
>Amit.
>
>
>[1] http://www.intel.com/design/servers/boards/SE7210TP1-E/
>
>-- 
>Amit Shah
>http://amitshah.nav.to/
>
>
>
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>SF.Net email is sponsored by Shop4tech.com-Lowest price on Blank Media
>100pk Sonic DVD-R 4x for only $29 -100pk Sonic DVD+R for only $33
>Save 50% off Retail on Ink & Toner - Free Shipping and Free Gift.
>http://www.shop4tech.com/z/Inkjet_Cartridges/9_108_r285
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>Linux-hotplug-devel@lists.sourceforge.net
>https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel
>


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