* [PATCH] powerpc/mpic: Remove WHOAMI readback after EOI
@ 2015-03-24 10:43 Bogdan Purcareata
2015-05-13 12:23 ` Purcareata Bogdan
0 siblings, 1 reply; 3+ messages in thread
From: Bogdan Purcareata @ 2015-03-24 10:43 UTC (permalink / raw)
To: linuxppc-dev, scottwood, segher, benh; +Cc: linux-kernel
After previous discussions regarding the subject [1][2], there's no clear
explanation or reason why the call was needed in the first place. The sensible
argument is some sort of synchronization between the CPU and the MPIC, which
hasn't been pointed out precisely and is no longer required (at least on BookE
platforms).
The benefit of this change is saving a MMIO trap per interrupt when running in a
KVM guest.
[1] https://patchwork.ozlabs.org/patch/429098/
[2] https://patchwork.ozlabs.org/patch/433557/
Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com>
---
arch/powerpc/sysdev/mpic.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index bbfbbf2..045e72a9 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -655,7 +655,6 @@ static inline struct mpic * mpic_from_irq_data(struct irq_data *d)
static inline void mpic_eoi(struct mpic *mpic)
{
mpic_cpu_write(MPIC_INFO(CPU_EOI), 0);
- (void)mpic_cpu_read(MPIC_INFO(CPU_WHOAMI));
}
/*
--
2.1.4
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] powerpc/mpic: Remove WHOAMI readback after EOI
2015-03-24 10:43 [PATCH] powerpc/mpic: Remove WHOAMI readback after EOI Bogdan Purcareata
@ 2015-05-13 12:23 ` Purcareata Bogdan
2015-05-13 16:33 ` Scott Wood
0 siblings, 1 reply; 3+ messages in thread
From: Purcareata Bogdan @ 2015-05-13 12:23 UTC (permalink / raw)
To: Bogdan Purcareata, linuxppc-dev, scottwood, segher, benh; +Cc: linux-kernel
Ping?
On 24.03.2015 12:43, Bogdan Purcareata wrote:
> After previous discussions regarding the subject [1][2], there's no clear
> explanation or reason why the call was needed in the first place. The sensible
> argument is some sort of synchronization between the CPU and the MPIC, which
> hasn't been pointed out precisely and is no longer required (at least on BookE
> platforms).
>
> The benefit of this change is saving a MMIO trap per interrupt when running in a
> KVM guest.
>
> [1] https://patchwork.ozlabs.org/patch/429098/
> [2] https://patchwork.ozlabs.org/patch/433557/
>
> Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com>
> ---
> arch/powerpc/sysdev/mpic.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
> index bbfbbf2..045e72a9 100644
> --- a/arch/powerpc/sysdev/mpic.c
> +++ b/arch/powerpc/sysdev/mpic.c
> @@ -655,7 +655,6 @@ static inline struct mpic * mpic_from_irq_data(struct irq_data *d)
> static inline void mpic_eoi(struct mpic *mpic)
> {
> mpic_cpu_write(MPIC_INFO(CPU_EOI), 0);
> - (void)mpic_cpu_read(MPIC_INFO(CPU_WHOAMI));
> }
>
> /*
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] powerpc/mpic: Remove WHOAMI readback after EOI
2015-05-13 12:23 ` Purcareata Bogdan
@ 2015-05-13 16:33 ` Scott Wood
0 siblings, 0 replies; 3+ messages in thread
From: Scott Wood @ 2015-05-13 16:33 UTC (permalink / raw)
To: Purcareata Bogdan; +Cc: linuxppc-dev, Bogdan Purcareata, linux-kernel
On Wed, 2015-05-13 at 15:23 +0300, Purcareata Bogdan wrote:
> Ping?
>
> On 24.03.2015 12:43, Bogdan Purcareata wrote:
> > After previous discussions regarding the subject [1][2], there's no clear
> > explanation or reason why the call was needed in the first place. The sensible
> > argument is some sort of synchronization between the CPU and the MPIC, which
> > hasn't been pointed out precisely and is no longer required (at least on BookE
> > platforms).
> >
> > The benefit of this change is saving a MMIO trap per interrupt when running in a
> > KVM guest.
> >
> > [1] https://patchwork.ozlabs.org/patch/429098/
> > [2] https://patchwork.ozlabs.org/patch/433557/
> >
> > Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com>
> > ---
> > arch/powerpc/sysdev/mpic.c | 1 -
> > 1 file changed, 1 deletion(-)
Don't top-post.
This is commit 56302c53d3dc477b8360954fc92c1dfc4fc0ec54 in Linus's tree.
-Scott
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-03-24 10:43 [PATCH] powerpc/mpic: Remove WHOAMI readback after EOI Bogdan Purcareata
2015-05-13 12:23 ` Purcareata Bogdan
2015-05-13 16:33 ` Scott Wood
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