Help with Dreamcast flash devices

Help with Dreamcast flash devices

[adr]

I wonder if someone here might help me.

I am one of the (too) small team of developers on the Linux on Dreamcast 
project (http://sourceforge.net/projects/linuxdc). I am currently working on 
developing a driver for the flash memory devices available for this machine.

Someone else started work on this months ago, but nothing has been done for 
ages, so I'm hacking at it now.

The flash memory on the DC is "smart" - ie it's attached to an 8-bit 
micro-controller. The device communicates with the rest of the system via a 
high speed serial ("maple") protocol. The flash is not mapped into the sh4 
(main cpu) physical memory at all. (http://mc.pp.se/dc/vms/index.html leads 
to more information for those interested).

Well, the long and the short of it is that I am somewhat at sea here. Are 
there any similar mtd devices I can look at?

Is there an explanation anywhere of how mapping works and how to 'virtual' map 
something which isn't in the physical map at all?

Any other ideas (random or now) about how to make this work? Currently the 
driver fails on mapping.

Adrian

RE: Help with Dreamcast flash devices

[Gregg C Levine]

Hello from Gregg C Levine
Funny... I bought my DC console, on, or around the beginning of December
of last year, superficially for trying out either Linux, or say another
related OS, on it. So far, I have tracked down the usual collection of
resources, including several pages on a site that I find mentioned on
the ECOS pages, at Sources Red Hat. Have you had any luck getting your
DC to startup using Linux? And can you send me a CD, to try out, if I
were to supply my hard mail address? E-mail me off list with your
details. I regret that I can not actually support your flash problems.
-------------------
Gregg C Levine hansolofalcon@worldnet.att.net
------------------------------------------------------------
"The Force will be with you...Always." Obi-Wan Kenobi
"Use the Force, Luke."  Obi-Wan Kenobi
(This company dedicates this E-Mail to General Obi-Wan Kenobi )
(This company dedicates this E-Mail to Master Yoda )



> -----Original Message-----
> From: linux-mtd-admin@lists.infradead.org [mailto:linux-mtd-
> admin@lists.infradead.org] On Behalf Of adr
> Sent: Sunday, August 11, 2002 2:08 PM
> To: linux-mtd@lists.infradead.org
> Subject: Help with Dreamcast flash devices
> 
> I wonder if someone here might help me.
> 
> I am one of the (too) small team of developers on the Linux on
Dreamcast
> project (http://sourceforge.net/projects/linuxdc). I am currently
working on
> developing a driver for the flash memory devices available for this
machine.
> 
> Someone else started work on this months ago, but nothing has been
done for
> ages, so I'm hacking at it now.
> 
> The flash memory on the DC is "smart" - ie it's attached to an 8-bit
> micro-controller. The device communicates with the rest of the system
via a
> high speed serial ("maple") protocol. The flash is not mapped into the
sh4
> (main cpu) physical memory at all. (http://mc.pp.se/dc/vms/index.html
leads
> to more information for those interested).
> 
> Well, the long and the short of it is that I am somewhat at sea here.
Are
> there any similar mtd devices I can look at?
> 
> Is there an explanation anywhere of how mapping works and how to
'virtual' map
> something which isn't in the physical map at all?
> 
> Any other ideas (random or now) about how to make this work? Currently
the
> driver fails on mapping.
> 
> Adrian
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: Help with Dreamcast flash devices

[Jörn Engel]

On Sun, 11 August 2002 19:08:06 +0100, adr wrote:
> I am one of the (too) small team of developers on the Linux on Dreamcast 
> project (http://sourceforge.net/projects/linuxdc). I am currently working on 
> developing a driver for the flash memory devices available for this machine.
> 
> Someone else started work on this months ago, but nothing has been done for 
> ages, so I'm hacking at it now.
> 
> The flash memory on the DC is "smart" - ie it's attached to an 8-bit 
> micro-controller. The device communicates with the rest of the system via a 
> high speed serial ("maple") protocol. The flash is not mapped into the sh4 
> (main cpu) physical memory at all. (http://mc.pp.se/dc/vms/index.html leads 
> to more information for those interested).
> 
> Well, the long and the short of it is that I am somewhat at sea here. Are 
> there any similar mtd devices I can look at?
> 
> Is there an explanation anywhere of how mapping works and how to 'virtual' map 
> something which isn't in the physical map at all?
> 
> Any other ideas (random or now) about how to make this work? Currently the 
> driver fails on mapping.

My best guess would be to create something similar to the slram
driver, but with different guts. Basically, you have to write some
functions for reading and writing to the flash through the controller.
Erasing, locking and so on might work directly, or it might have to be
emulated.
This should be some two weeks of work, if you trust my estimates more
than I do. :)

Just out of curiosity: Is the flash really only 128kiB? If so, will
there be anything much in it, except for the bootloader? And if even
that is true, shouldn't a userspace flasher do the job just as well?

Jörn

-- 
A surrounded army must be given a way out.
-- Sun Tzu

Re: Help with Dreamcast flash devices

[adr]

On Sunday 11 Aug 2002 8:52 pm, Jörn Engel wrote:

>
> Just out of curiosity: Is the flash really only 128kiB? If so, will
> there be anything much in it, except for the bootloader? And if even
> that is true, shouldn't a userspace flasher do the job just as well?
>
> Jrn

Well, you can get bigger lumps of flash, but they can only be addressed in 
128k lumps.

It won't even have a booloader - as there is no way to get the DC to boot from 
the flash. It's just a challenge, that's all :->

Re: Help with Dreamcast flash devices

[adr]

On Sunday 11 Aug 2002 8:52 pm, Jörn Engel wrote:

>
> My best guess would be to create something similar to the slram
> driver, but with different guts. 


I've looked at slram.c - but don't really understand what it is for. What sort 
of device is it?

Adrian

Re: Help with Dreamcast flash devices

[Jörn Engel]

On Mon, 12 August 2002 21:54:19 +0100, adr wrote:
> On Sunday 11 Aug 2002 8:52 pm, Jörn Engel wrote:
> > My best guess would be to create something similar to the slram
> > driver, but with different guts. 
> 
> I've looked at slram.c - but don't really understand what it is for.
> What sort of device is it?

Physical RAM, plain and simple. Usually system memory, after passing a
"mem=a_little_less_than_availlable" command line option. Sometimes
NVRAM that is mapped into the physical memory address range.

Jörn

-- 
"Security vulnerabilities are here to stay."
-- Scott Culp, Manager of the Microsoft Security Response Center, 2001

Re: Help with Dreamcast flash devices

[David Woodhouse]

mtd@mcmen.demon.co.uk said:
>  Well, the long and the short of it is that I am somewhat at sea here.
> Are  there any similar mtd devices I can look at?

> Is there an explanation anywhere of how mapping works and how to
> 'virtual' map  something which isn't in the physical map at all? 

Your map functions must read and write words to the flash, and provide 
methods for copying chunks of data from the flash. That's about it.

They may not sleep. Is that a problem?

--
dwmw2