Subject: ARM v4 support in proc-arm720.S ?

From: "Cliff Brake" <[email-masked]>
Date: Mon, 3 Jul 2000 14:18:36 -0400

The proc-arm720.S data abort code is having some trouble with a "ldrh
r3, [r12, #14]" instruction found in the ld-linux-so.2 library file I'm
using (from a StrongArm ramdisk image).  It seems that the ARM v4
instructions are not supported in the proc-arm720.S file.  I have formed
the following conclusions -- please correct me if they are wrong:

1)  The ARM7TDMI is a v4 processor (which is used in the ARM720 core)
2)  The SA1100 and SA1110 are v4 processors.
3)  User level code should be binary compatible between ARM7TDMI and
SA11x0 processors (including library files such as ld-linux-so.2).

The StrongArm cpu_sa110[0]_data_abort function is much simpler than the
cpu_arm720_data_abort function.  Does the StrongArm magically fix up the
registers during a data abort in hardware that have to be fixed up in
software on the ARM720?

If the above analysis is correct, are there plans to update
proc-arm720.S to v4?

Cliff

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From: Russell King - ARM Linux Admin <[email-masked]>
Date: Mon, 3 Jul 2000 21:45:11 +0100 (BST)

Cliff Brake writes:
> cpu_arm720_data_abort function.

Because the StrongARM implements the "early abort" option of the v4
architecture, whereas the ARM7 cores implement the "late abort" option.

> Does the StrongArm magically fix up the registers during a data abort
> in hardware that have to be fixed up in software on the ARM720?

No fixup required, since the StrongARM does not write a modified base
register value back.

> If the above analysis is correct, are there plans to update

The arm720 file is v4 - its just missing the required code for the
half word and signed byte loads.  If someone's willing to implement
it... (hint hint)
   _____
  |_____| ------------------------------------------------- ---+---+-
  |   |        Russell King       [email-masked]      --- ---
  | | | |            http://www.arm.linux.org.uk/            /  /  |
  | +-+-+                                                     --- -+-
  /   |               THE developer of ARM Linux              |+| /|\
 /  | | |                                                     ---  |
    +-+-+ -------------------------------------------------  /\\\  |

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From: "Cliff Brake" <[email-masked]>
Date: Mon, 3 Jul 2000 17:20:03 -0400

>-----Original Message-----
>From: Russell King - ARM Linux Admin [mailto:[email-masked]]
>Sent: Monday, July 03, 2000 4:45 PM
>To: Cliff Brake
>Cc: "Linux-Arm-Kernel (E-mail)"
>Subject: Re: ARM v4 support in proc-arm720.S ?
>
>

ok, I'll add the half word/signed byte stuff.

Cliff