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authorMarc Zyngier <marc.zyngier@arm.com>2018-05-31 16:21:43 +0100
committerMarc Zyngier <marc.zyngier@arm.com>2018-07-27 10:01:24 +0100
commit30800b3a1fb14c6f143db5616a4aaea9fef94af3 (patch)
tree48bcc72a292e8e87a2b7465ac7e6b35a8800c875
parent12b2905af183c931bedcab4292c81d3a415e080f (diff)
downloadlinux-30800b3a1fb14c6f143db5616a4aaea9fef94af3.tar.bz2
irqchip/gic-v3-its: Reduce minimum LPI allocation to 1 for PCI devices
Allocating a minimum of 32 LPIs per PCI device, let's reduce it to be just 1, as most devices do not need that many interrupts. We still have to special-case DevID 0, as there is plenty of broken HW around where the PCI RID is not presented as a DevID to the ITS, and all the devices are presented as DevID 0. In this case, we keep the 32 minimal allocation. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
-rw-r--r--drivers/irqchip/irq-gic-v3-its-pci-msi.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/drivers/irqchip/irq-gic-v3-its-pci-msi.c b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
index 75c3cafabc6a..8d6d009d1d58 100644
--- a/drivers/irqchip/irq-gic-v3-its-pci-msi.c
+++ b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
@@ -66,7 +66,7 @@ static int its_pci_msi_prepare(struct irq_domain *domain, struct device *dev,
{
struct pci_dev *pdev, *alias_dev;
struct msi_domain_info *msi_info;
- int alias_count = 0;
+ int alias_count = 0, minnvec = 1;
if (!dev_is_pci(dev))
return -EINVAL;
@@ -86,9 +86,17 @@ static int its_pci_msi_prepare(struct irq_domain *domain, struct device *dev,
/* ITS specific DeviceID, as the core ITS ignores dev. */
info->scratchpad[0].ul = pci_msi_domain_get_msi_rid(domain, pdev);
- /* Allocate at least 32 MSIs, and always as a power of 2 */
+ /*
+ * Always allocate a power of 2, and special case device 0 for
+ * broken systems where the DevID is not wired (and all devices
+ * appear as DevID 0). For that reason, we generously allocate a
+ * minimum of 32 MSIs for DevID 0. If you want more because all
+ * your devices are aliasing to DevID 0, consider fixing your HW.
+ */
nvec = max(nvec, alias_count);
- nvec = max_t(int, 32, roundup_pow_of_two(nvec));
+ if (!info->scratchpad[0].ul)
+ minnvec = 32;
+ nvec = max_t(int, minnvec, roundup_pow_of_two(nvec));
return msi_info->ops->msi_prepare(domain->parent, dev, nvec, info);
}