From: Andrew Johnson <anj@aps.anl.gov>
To: linuxppc-embedded@lists.linuxppc.org
Subject: Re: EPIC Vs OpenPIC Vs MontaVista
Date: Fri, 02 Nov 2001 10:03:23 -0600 [thread overview]
Message-ID: <3BE2C3CB.DB73EF49@aps.anl.gov> (raw)
In-Reply-To: 20011102134754.29665.qmail@mailweb16.rediffmail.com
Sarnath Kannan wrote:
>
> The reason for assigning vector of 16 to PCI
> interrupts is because each entry in the "Interrupt Source" is 32 bytes long, 16 * 32 = 512 = 0x200
> which equals the difference in offsets between
> the std openPIC layout and EPIC register layout.
> This 16 has got NOTHING TO DO with NUM_8259_INTERRUPTS.
> But Mvista code seems to assume that this feature
> is because of NUM_8259_INTERRUPTS. ( See the
> #define for SANDPOINT_SIO_IRQ ).
... unless the register layout for the EPIC was designed to allow an
external i8259 to be inserted into the gap, which ISTR is done on some
boards. I don't know for sure and I might be completely confused about
that, but there must have been some reason why the EPIC was designed like
that.
Just throwing that idea into the pot...
- Andrew
--
Perfection is reached, not when there is no longer anything to add,
but when there is no longer anything to take away.
- Antoine de Saint-Exupery
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2001-11-02 16:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-11-02 13:47 EPIC Vs OpenPIC Vs MontaVista Sarnath Kannan
2001-11-02 14:00 ` Dag Nygren
2001-11-02 16:03 ` Andrew Johnson [this message]
-- strict thread matches above, loose matches on Subject: below --
2001-11-02 15:25 Sarnath Kannan
2001-11-02 17:41 ` Mark A. Greer
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