From 30800b3a1fb14c6f143db5616a4aaea9fef94af3 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Thu, 31 May 2018 16:21:43 +0100 Subject: [PATCH] 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 --- drivers/irqchip/irq-gic-v3-its-pci-msi.c | 14 +++++++++++--- 1 file 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); } -- 2.11.0