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ppc440_pcix: Improve comment for IRQ mapping

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The code mapping all PCI interrupts to a single CPU IRQ works but is
not trivial so document it in a comment.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-Id: <c25c0310510672b58466e795fd701e65e8f1ff97.1609636173.git.balaton@eik.bme.hu>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
BALATON Zoltan via 2021-01-03 02:09:33 +01:00 committed by David Gibson
parent 038da2adf0
commit 2a9cf49598
1 changed files with 9 additions and 2 deletions
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11
hw/ppc/ppc440_pcix.c
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@ -415,8 +415,15 @@ static void ppc440_pcix_reset(DeviceState *dev)
s->sts = 0;
}
/* All pins from each slot are tied to a single board IRQ.
* This may need further refactoring for other boards. */
/*
* All four IRQ[ABCD] pins from all slots are tied to a single board
* IRQ, so our mapping function here maps everything to IRQ 0.
* The code in pci_change_irq_level() tracks the number of times
* the mapped IRQ is asserted and deasserted, so if multiple devices
* assert an IRQ at the same time the behaviour is correct.
*
* This may need further refactoring for boards that use multiple IRQ lines.
*/
static int ppc440_pcix_map_irq(PCIDevice *pci_dev, int irq_num)
{
trace_ppc440_pcix_map_irq(pci_dev->devfn, irq_num, 0);