From owner-freebsd-alpha  Wed Jan 27 04:33:43 1999
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Date: Wed, 27 Jan 1999 13:32:25 +0100 (MET)
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From: Joerg Czeranski <jc@joerch.org>
To: shimon@simon-shapiro.org
Cc: freebsd-alpha@FreeBSD.ORG
In-Reply-To: <XFMail.990126052812.shimon@simon-shapiro.org>
Subject: Re: Alpha Driver Help Requested
Sender: owner-freebsd-alpha@FreeBSD.ORG
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X-Loop: FreeBSD.org

Simon Shapiro wrote:
> *  The driver panics on trap entry 0x4 (unaligned access fault).  This
>    happens in the following code snippet:
> 
>         dpt_outl(dpt, HA_WDMAADDR, cmd_busaddr);
> 
>    All the arguments are of the correct type.

And:
> I narrowed down the failure to line 467 in sys/alpha/bus.h which simply
> says:
> 
>         outl(bsh + offset, value);

And:
> fatal kernel trap:
> 
>     trap entry = 0x4 (unaligned access fault)
>     a0         = 0xfffffca900010192
>     a1         = 0x2c
>     a2         = 0x11
>     pc         = 0xfffffc00004a77bc
>     ra         = 0xfffffc000034f958
>     curproc    = 0

Decoding the values:

/usr/src/sys/dev/dpt/dpt.h:      #define HA_WDMAADDR 0x02
             alpha/pci/ciareg.h: #define CIA_EV56_BWIO 0x8900000000UL

The base address of the DPT probably is 0x10190.

Thus a0 is a bus space address (for use with the Byte/Word/eXtension of
>= EV56 implementations) aligned to a word (16bit), but it is used by
outl for a longword (32bit) access.  This results in the unaligned
access fault.

Either a 32 bit access wasn't intended (it overlaps with HW_WCODE and
HW_WCODE2 anyway, maybe a bug?) or it must be split into two 16 bit
writes.

joerch

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