Re: [PATCH 04/17] powerpc: mpic: use IRQCHIP_SKIP_SET_WAKE instead of redundant mpic_irq_set_wake

[Scott Wood <scottwood@freescale.com>]

On Mon, 2015-09-21 at 16:47 +0100, Sudeep Holla wrote:
> mpic_irq_set_wake return -ENXIO for non FSL MPIC and sets IRQF_NO_SUSPEND
> flag for FSL ones. enable_irq_wake already returns -ENXIO if irq_set_wak
> is not implemented. Also there's no need to set the IRQF_NO_SUSPEND flag
> as it doesn't guarantee wakeup for that interrupt.
> 
> This patch removes the redundant mpic_irq_set_wake and sets the
> IRQCHIP_SKIP_SET_WAKE for only FSL MPIC.
> 
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Scott Wood <scottwood@freescale.com>
> Cc: Hongtao Jia <hongtao.jia@freescale.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  arch/powerpc/sysdev/mpic.c | 23 ++++-------------------
>  1 file changed, 4 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
> index 537e5db85a06..123e43612f0a 100644
> --- a/arch/powerpc/sysdev/mpic.c
> +++ b/arch/powerpc/sysdev/mpic.c
> @@ -924,22 +924,6 @@ int mpic_set_irq_type(struct irq_data *d, unsigned int 
> flow_type)
>       return IRQ_SET_MASK_OK_NOCOPY;
>  }
>  
> -static int mpic_irq_set_wake(struct irq_data *d, unsigned int on)
> -{
> -     struct irq_desc *desc = container_of(d, struct irq_desc, irq_data);
> -     struct mpic *mpic = mpic_from_irq_data(d);
> -
> -     if (!(mpic->flags & MPIC_FSL))
> -             return -ENXIO;
> -
> -     if (on)
> -             desc->action->flags |= IRQF_NO_SUSPEND;
> -     else
> -             desc->action->flags &= ~IRQF_NO_SUSPEND;
> -
> -     return 0;
> -}
> -
>  void mpic_set_vector(unsigned int virq, unsigned int vector)
>  {
>       struct mpic *mpic = mpic_from_irq(virq);
> @@ -977,7 +961,6 @@ static struct irq_chip mpic_irq_chip = {
>       .irq_unmask     = mpic_unmask_irq,
>       .irq_eoi        = mpic_end_irq,
>       .irq_set_type   = mpic_set_irq_type,
> -     .irq_set_wake   = mpic_irq_set_wake,
>  };
>  
>  #ifdef CONFIG_SMP
> @@ -992,7 +975,6 @@ static struct irq_chip mpic_tm_chip = {
>       .irq_mask       = mpic_mask_tm,
>       .irq_unmask     = mpic_unmask_tm,
>       .irq_eoi        = mpic_end_irq,
> -     .irq_set_wake   = mpic_irq_set_wake,
>  };
>  
>  #ifdef CONFIG_MPIC_U3_HT_IRQS
> @@ -1283,8 +1265,11 @@ struct mpic * __init mpic_alloc(struct device_node 
> *node,
>               flags |= MPIC_NO_RESET;
>       if (of_get_property(node, "single-cpu-affinity", NULL))
>               flags |= MPIC_SINGLE_DEST_CPU;
> -     if (of_device_is_compatible(node, "fsl,mpic"))
> +     if (of_device_is_compatible(node, "fsl,mpic")) {
>               flags |= MPIC_FSL | MPIC_LARGE_VECTORS;
> +             mpic_irq_chip.flags |= IRQCHIP_SKIP_SET_WAKE;
> +             mpic_tm_chip.flags |= IRQCHIP_SKIP_SET_WAKE;
> +     }

What difference does IRQCHIP_SKIP_SET_WAKE make in the absence of an 
.irq_set_wake() callback?

This is basically repealing commit 5ff04b7287d87c1db7 ("powerpc/mpic: add 
irq_set_wake support").  Wang Dongsheng, can you explain why that patch was 
needed?

-Scott