Messages in this thread Patch in this message | | | Date | Thu, 22 Dec 2011 17:35:50 +0100 | From | Jens Rottmann <> | Subject | [PATCH] cs5535-clockevt: allow the MFGPT IRQ to be shared |
| |
cs5535-clockevt: allow the MFGPT IRQ to be shared
Shared timer IRQs are not a good solution, however the Geode platform has no APIC, IRQs are a scarce resource and there is no technical reason to forbid it rightaway. Increased latencies and overhead due to sharing are still better than a driver refusing to load.
Signed-off-by: Jens Rottmann <JRottmann@LiPPERTEmbedded.de> ---
Hi,
I tested this a bit longer, this time with MFGPT IRQ actually being triggered, with cs5535-clockevt driver loaded first or second when sharing the IRQ, with some CPU load or without.
I didn't encounter any negative effects of this change. I did have suspend problems with cs5535-clockevt, but that was in no way different from before I applied this patch, it's an unrelated BIOS issue.
Thomas Gleixner wrote: > No, you can share a timer irq. The other drivers don't have the SHARED > flag set because they are on exclusive irq lines, ...
Is this an ACK?
> shared irqs suck and you figure that out once you try to > use that shared timer irq on a preempt-rt enabled kernel.
Or a NACK? :-| (I did address this in the commit log.)
The kernel I tested with was 3.2-rc6, CONFIG_SMP=y and CONFIG_PREEMPT=y. As I said, I didn't notice anything bad happening.
Thanks and have a nice christmas holiday, Jens
--- linux-3.2-rc6/drivers/clocksource/cs5535-clockevt.c +++ allow_shared_mfgpt_irq/drivers/clocksource/cs5535-clockevt.c @@ -133,7 +133,7 @@ static irqreturn_t mfgpt_tick(int irq, v static struct irqaction mfgptirq = { .handler = mfgpt_tick, - .flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER, + .flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER | IRQF_SHARED, .name = DRV_NAME, }; _
| |