From: Will Wagner <will_wagner@carallon.com>
To: ecos-discuss@sources.redhat.com
Subject: [ECOS] Dual Port RAM on MPC8xx
Date: Wed, 20 Apr 2005 10:50:00 -0000 [thread overview]
Message-ID: <42663119.306@carallon.com> (raw)
I'm trying to understand how the allocation of DPRAM is done in the
function _mpc8xx_allocBd in cpm.c.
Can someone explain why nextBD is initialised as:
static short *nextBd = (short *)(CYGHWR_HAL_VSR_TABLE + 0x1F0);
Presumably this is so that redboot and an application can cooperate when
using the DPRAM? Why is this address chosen and when is it's contents
ever initialised?
Presumably it may not have been initialised as in _mpc8xx_allocBd there
is this code:
if ((bd < QUICC_BD_BASE) || (bd > QUICC_BD_END)) {
// Most likely not set up - make a guess :-(
bd = *nextBd = QUICC_BD_BASE+0x400;
}
I guess this is starting 0x400 into the DPRAM so that an apllication
doesn't reuse any DPRAM used by redboot? Is this correct? I can find
where redboot ever initialises this memory so I can't see how it works.
Any help in understanding this is much appreciated.
Will Wagner
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next reply other threads:[~2005-04-20 10:35 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-20 10:50 Will Wagner [this message]
2005-04-20 10:53 ` Gary Thomas
2005-04-20 12:10 ` Will Wagner
2005-04-20 12:56 ` Gary Thomas
2005-04-21 15:25 ` [ECOS] Serial Port in non-blocking mode Gatien Gillon
2005-04-21 16:50 ` Andrew Lunn
2005-04-21 18:43 ` Gatien Gillon
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