The ARM GICv3 TRM describes that the ITLinesNumber field of GICD_TYPER
register:
"indicates the maximum SPI INTID that the GIC implementation supports"
As SPI #0 is absolute IRQ #32, the max SPI INTID should have accounted
for the internal 16x SGI's and 16x PPI's. However, the original GICv3
model subtracted off the SGI/PPI. Cosmetically this can be seen at OS
boot (Linux) showing 32 shy of what should be there, i.e.:
[ 0.000000] GICv3: 224 SPIs implemented
Though in hw/arm/virt.c, the machine is configured for 256 SPI's. ARM
virt machine likely doesn't have a problem with this because the upper
32 IRQ's don't actually have anything meaningful wired. But, this does
become a functional issue on a custom use case which wants to make use
of these IRQ's. Additionally, boot code (i.e. TF-A) will only init up
to the number (blocks of 32) that it believes to actually be there.
Signed-off-by: Luke Starrett <lukes@xsightlabs.com>
---
hw/intc/arm_gicv3_dist.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/intc/arm_gicv3_dist.c b/hw/intc/arm_gicv3_dist.c
index eea0368118..d599fefcbc 100644
--- a/hw/intc/arm_gicv3_dist.c
+++ b/hw/intc/arm_gicv3_dist.c
@@ -390,9 +390,9 @@ static bool gicd_readl(GICv3State *s, hwaddr offset,
* MBIS == 0 (message-based SPIs not supported)
* SecurityExtn == 1 if security extns supported
* CPUNumber == 0 since for us ARE is always 1
- * ITLinesNumber == (num external irqs / 32) - 1
+ * ITLinesNumber == (((max SPI IntID + 1) / 32) - 1)
*/
- int itlinesnumber = ((s->num_irq - GIC_INTERNAL) / 32) - 1;
+ int itlinesnumber = (s->num_irq / 32) - 1;
/*
* SecurityExtn must be RAZ if GICD_CTLR.DS == 1, and
* "security extensions not supported" always implies DS == 1,