Re: [RFC v3 1/9] arm: fiq: arbitrary mappings from IRQ to FIQ virqs

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Thu, Jun 05, 2014 at 10:53:06AM +0100, Daniel Thompson wrote:
>  static int fiq_def_op(void *ref, int relinquish)
>  {
> -	if (!relinquish)
> +	if (!relinquish) {
> +		unsigned offset = FIQ_OFFSET;
> +		no_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
>  		set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn));
> +	}
...
>  void __init init_FIQ(int start)
>  {
> -	unsigned offset = FIQ_OFFSET;
> -	no_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
>  	fiq_start = start;
>  }

This is wrong - when the default handler is "reinstalled", this change has
the effect that we read the first instruction of the existing handler, and
then write that same instruction back, rather than replacing the first
instruction with the value that was there at boot.

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