Messages in this thread Patch in this message | | | From | Marc Zyngier <> | Subject | [PATCH] clocksource/arm_arch_timer: Force per-CPU interrupt to trigger on level-high | Date | Mon, 9 May 2016 14:06:37 +0100 |
| |
The ARM architected timer produces level-triggered interrupts (this is mandated by the architecture). Unfortunately, most device-trees get this wrong, and expose an edge-triggered interrupt.
Until now, this wasn't too much an issue, as the programming of the trigger would fail (the corresponding PPI cannot be reconfigured), and the kernel would be happy with this. But we're about to change this, and trust DT a lot if the driver doesn't provide its own trigger information. In that context, the timer breaks badly.
While we do need to fix the DTs, there is also some userspace out there (kvmtool) that generates the same kind of broken DT on the fly, and that will completely break with newer kernels.
As a safety measure, and to keep buggy software alive as well as buying us some time to fix DTs all over the place, let's enforce the interrupt trigger in the timer driver. This doesn't cost us anything, and ensures that this will work in all situations, broken DT or not.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> --- drivers/clocksource/arm_arch_timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c index 5152b38..fdf367ae 100644 --- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -366,7 +366,7 @@ static int arch_timer_setup(struct clock_event_device *clk) { __arch_timer_setup(ARCH_CP15_TIMER, clk); - enable_percpu_irq(arch_timer_ppi[arch_timer_uses_ppi], 0); + enable_percpu_irq(arch_timer_ppi[arch_timer_uses_ppi], IRQF_TRIGGER_HIGH); if (arch_timer_has_nonsecure_ppi()) enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0); -- 2.1.4
| |