Subject: [PATCH 00/16 v9] omap 8250 based uart + DMA

From: [email-masked] (Sebastian Andrzej Siewior)
Date: Wed, 17 Sep 2014 10:38:52 +0200

On 09/16/2014 11:30 PM, Tony Lindgren wrote:
> Found one more issue when booting on 2420 n8x0, maybe something to do
> with runtime PM?
To some degree, yes.

> [    4.770507] Internal error: Oops - undefined instruction: 0 [#1]
SMP ARM

  e3a02000        mov     r2, #0
  ee072fba        mcr     15, 0, r2, cr7, cr10, {5}
  e3a01001        mov     r1, #1
  f5d3f000        pld     [r3]
=>e1d30f9f        ldrexb  r0, [r3]

That ldrexb is part of the xchg() function in serial8250_rpm_get_tx().
So it looks like 2420 n8x0 does not understand ldrexb but the inline
assembly decided that it should.

This OMAP2420 should be ARM1136 / ARMv6. The ARM1136J(F)-S TRM says for
ldrexb: "This command is only available from the rev1 (r1p0) release of
the ARM1136JF-S processor."

So it looks like the CPU should know what to do when this opcode comes
around.

> Regards,
> Tony

Sebastian