Messages in this thread | | | Subject | Re: [PATCH 4/4] irqchip: imgpdc: Pass on peripheral mask/unmasks to the parent | From | Ed Blake <> | Date | Thu, 5 Oct 2017 17:42:50 +0100 |
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On 05/10/17 16:43, Ed Blake wrote: > On 05/10/17 16:26, James Hogan wrote: >> On Thu, Oct 05, 2017 at 03:48:53PM +0100, Ed Blake wrote: >>> I'm not sure how this is supposed to work, but the issue seems to be >>> that without this patch the parent irq isn't being masked. This is >>> causing the parent handler (MIPS GIC in this case) to be called >>> continuously. This leads to the PDC irq being masked each time, but not >>> the parent irq. This is the callstack: >>> >>> "irq-imgpdc.c"::perip_irq_mask >>> mask_ack_irq >>> handle_level_irq >>> generic_handle_irq_desc >>> generic_handle_irq >>> generic_handle_irq_desc >>> generic_handle_irq >>> gic_handle_shared_int >>> gic_handle_local_int >>> "irq-mips-gic.c"::gic_irq_dispatch >>> generic_handle_irq_desc >>> generic_handle_irq >>> do_IRQ >>> plat_irq_dispatch() >> Right, yeh it shouldn't technically be masked by the parent (contrary to >> what I said above) because its a chained handler, i.e. as far as the >> kernel knows there could be other IRQs coming through that GIC pin that >> would also get masked. >> >> (though IIRC the perip IRQs can wake, but then they go straight out to >> separate dedicated IRQ pins into the main IRQ chip, i.e. the GIC in this >> case). > That's right, each of the PDC peripherals (RTC, WD, IR) has a dedicated > IRQ to the parent, and the sys wakes are muxed onto a single IRQ. >> I think its worth understanding the root cause here though. Disabling >> routing of an IRQ fundamentally should deassert it. Is it an actual >> hardware bug that has reached silicon? > So you think the PDC->parent IRQ must not be being de-asserted when > IRQ_ROUTE is cleared? I hadn't considered this and thought it was some > persistence in the GIC due to not being masked / ack'd there. Is that > possible? I'll discuss the possible IRQ_ROUTE issue with the hardware team.
OK, I've looked at the RTL and discussed it with the hardware team, and yes it's a bug. Clearing IRQ_ROUTE will not clear a PDC->GIC IRQ once asserted, the only way is to clear the RTC->PDC IRQ, which we can't do at this point as interrupts are disabled. So I think this method of propagating the mask to the parent is a reasonable workaround. Is it ok if I just modify the commit message and add comments to make it clear it's a workaround for a h/w bug?
Ed.
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