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Subject: RE: memory map madness
Date: Wed, 14 Mar 2007 17:47:28 -0700
Message-ID: <BB375AF679D4A34E9CA8DFA650E2B04E02D8F79F@onstor-exch02.onstor.net>
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Thread-Topic: memory map madness
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References: <20070314131829.514b95c7@ripper.onstor.net><BB375AF679D4A34E9CA8DFA650E2B04E02D8F746@onstor-exch02.onstor.net> <20070314173541.0d9e29f6@ripper.onstor.net>
From: "Brian Stark" <brian.stark@onstor.com>
To: "Andy Sharp" <andy.sharp@onstor.com>

That's right, we aren't using the same physical address for local memory
right now.  And the spaces you noted for the 512MB of local memory are
correct.  Sorry that the 256MB regions aren't contiguous.  Blame the PMC
mapping registers for this.

In an attempt to clear any confusion, let me address one of the
questions in your previous email.  From the point of view of the PMC,
SysAD and local memory are considered peripherals.  The CPU cores access
these peripherals with a virtual address that is then converted to a
physical address.  This physical address is then mapped by internal
registers to one of these peripherals, and it could then be remapped to
a different physical address.  This is often done to meet addressing
requirements of one of the chips attached to the same bus (e.g.
Marvell).

So, while you're correct that the CPU cores can't deal with peripherals
at the same physical address, it has no notion of the remapping that can
happen.  This remapping can result in two peripherals having the same
physical address from an overall system perspective, but since the
peripherals are isolated from each other by the internal remappers, this
doesn't matter.  From the perspective of the CPU cores, these
peripherals must live at different virtual and physical addresses (which
they do).

Hope I didn't confuse you any more.  If I did, then just read the first
paragraph in this reply again since we aren't using that upper 512MB of
space anyway!



> -----Original Message-----
> From: Andy Sharp=20
> Sent: Wednesday, March 14, 2007 5:36 PM
> To: Brian Stark
> Subject: Re: memory map madness
>=20
> On Wed, 14 Mar 2007 16:38:42 -0700 "Brian Stark"
> <brian.stark@onstor.com> wrote:
>=20
> > Andy,
>=20
> > I see your confusion about how there appears to be a=20
> physical address=20
> > conflict between the Marvell and local memory.  Keep in mind that=20
> > after all of the address translation and remapping stages=20
> inside the=20
> > PMC, it's possible that different peripherals, such as=20
> SysAD and local=20
> > memory, actually show the same physical address.  Since these=20
> > peripherals are isolated from each other, this is ok. =20
> Plus, we don't=20
> > actually use the virtual regions at 20000000 and 30000000 as noted=20
> > above.
>=20
> Nevermind that previous reply of mine, I was still suffering=20
> some confusion.  Basically, I take it that we aren't using=20
> the phys 4000.0000 address for local memory right now, we are=20
> using phys 0 thru (1000.0000 - 1) and 2000.0000 thru=20
> (3000.0000 - 1) for local memory, right?
>=20
> Cheers,
>=20
> a
>=20
> > Brian
> >=20
> >=20
> > > -----Original Message-----
> > > From: Andy Sharp
> > > Sent: Wednesday, March 14, 2007 1:18 PM
> > > To: Brian Stark
> > > Subject: memory map madness
> > >=20
> > > Hi Brian,
> > >=20
> > > I'm apparently having trouble reading the memory map pdf's.
> > >=20
> > > Bobcat\ Memory\ Map\ 3.pdf lists two different things at phys
> > > 0x4000.000: 256MB of local memory, and 256MB of Marvell memory.
> > >=20
> > >=20
> > > Bobcat\ Memory\ Map.pdf lists the marvell memory as starting at=20
> > > 0x5000.0000
> > >=20
> > > What's the real and true story of the memory map?
> > >=20
> > > Cheers,
> > >=20
> > > a
> > >=20
>=20
