[patch 2/4] [ARM] mmp: support marvell ARMADA610

[Russell King - ARM Linux]

On Mon, Jan 04, 2010 at 05:15:22AM -0500, Haojian Zhuang wrote:
> On Sun, Jan 3, 2010 at 11:27 PM, Eric Miao <eric.y.miao at gmail.com> wrote:
> >        .macro  get_irqnr_preamble, base, tmp
> >        mrc     p15, 0, \tmp, c0, c0, 0         @ CPUID
> >        mov     \tmp, \tmp, lsr #4
> >        and     \tmp, \tmp, #0xff0
> >        cmp     \tmp, #0x580
> 
> I have some concern on compressing 12-bit to 8-bit. Maybe it would not
> fit chips in future.

The spec for immediate constants is: any 32-bit constant, which may be
rotated by an even number of shift places to form a single 8-bit
constant.

So, 0x0ff00000 is legal (0xff rotated left 20).  0x07f800000 is not (0xff
rotated left 19).  0xfc000003 is legal (0xff rotated left 26).

This comes directly from the instruction coding, which is an 8-bit
constant plus a 4-bit shift.

> >        ldrne   \base, =ICU_AP_IRQ_SEL_INT_NUM
> >        ldreq   \base, =ICU_MMP2_PJ4_IRQ_SEL
> >        .endm
> >
> >        .macro  arch_ret_to_user, tmp1, tmp2
> >        .endm
> >
> >        .macro  get_irqnr_and_base, irqnr, irqstat, base, tmp
> >        ldr     \tmp, [\base]           @ AP INT SEL register
> >        and     \irqnr, \tmp, #0x3f
> >        tst     \tmp, #(1 << 6)
> >        .endm
> >
> It's wrong at here. Whatever we need to access ICU register in
> get_irqnr_and_base.
> 
>         .macro irq_handler
>         get_irqnr_preamble  r5, lr
> 1:     get_irqnr_and_base  r0, r6, r5, lr
>         ...
>         bne  asm_do_IRQ
> 
> If we just keep accessing ICU register in get_irqnr_preamble, we'll
> find lr register used in asm_do_IRQ. When the loop came back to
> get_irqnr_and_base(), we'll meet unpredicated value.

I don't see what you're getting at - Eric only uses the 'tmp' register
as a local temporary in each macro.  It's entirely local to that
macro, and each macro doesn't care what value it had previously.

The first thing that get_irqnr_and_base does is overwrite 'lr' with
the value from the INT SEL register.