From 0be8153cbc2af9a96e9ab8631fc3ba23bb52dbe3 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 8 May 2018 13:14:30 +0100 Subject: [PATCH] genirq/msi: Allow level-triggered MSIs to be exposed by MSI providers So far, MSIs have been used to signal edge-triggered interrupts, as a write is a good model for an edge (you can't "unwrite" something). On the other hand, routing zillions of wires in an SoC because you need level interrupts is a bit extreme. People have come up with a variety of schemes to support this, which involves sending two messages: one to signal the interrupt, and one to clear it. Since the kernel cannot represent this, we've ended up with side-band mechanisms that are pretty awful. Instead, let's acknoledge the requirement, and ensure that, under the right circumstances, the irq_compose_msg and irq_write_msg can take as a parameter an array of two messages instead of a pointer to a single one. We also add some checking that the compose method only clobbers the second message if the MSI domain has been created with the MSI_FLAG_LEVEL_CAPABLE flags. Signed-off-by: Marc Zyngier Signed-off-by: Thomas Gleixner Cc: Rob Herring Cc: Jason Cooper Cc: Ard Biesheuvel Cc: Srinivas Kandagatla Cc: Thomas Petazzoni Cc: Miquel Raynal Link: https://lkml.kernel.org/r/20180508121438.11301-2-marc.zyngier@arm.com --- include/linux/msi.h | 2 ++ kernel/irq/msi.c | 33 ++++++++++++++++++++++++--------- 2 files changed, 26 insertions(+), 9 deletions(-) diff --git a/include/linux/msi.h b/include/linux/msi.h index 1f1bbb5b4679..5839d8062dfc 100644 --- a/include/linux/msi.h +++ b/include/linux/msi.h @@ -289,6 +289,8 @@ enum { * MSI_FLAG_ACTIVATE_EARLY has been set. */ MSI_FLAG_MUST_REACTIVATE = (1 << 5), + /* Is level-triggered capable, using two messages */ + MSI_FLAG_LEVEL_CAPABLE = (1 << 6), }; int msi_domain_set_affinity(struct irq_data *data, const struct cpumask *mask, diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c index 2a8571f72b17..4ca2fd46645d 100644 --- a/kernel/irq/msi.c +++ b/kernel/irq/msi.c @@ -76,6 +76,19 @@ static inline void irq_chip_write_msi_msg(struct irq_data *data, data->chip->irq_write_msi_msg(data, msg); } +static void msi_check_level(struct irq_domain *domain, struct msi_msg *msg) +{ + struct msi_domain_info *info = domain->host_data; + + /* + * If the MSI provider has messed with the second message and + * not advertized that it is level-capable, signal the breakage. + */ + WARN_ON(!((info->flags & MSI_FLAG_LEVEL_CAPABLE) && + (info->chip->flags & IRQCHIP_SUPPORTS_LEVEL_MSI)) && + (msg[1].address_lo || msg[1].address_hi || msg[1].data)); +} + /** * msi_domain_set_affinity - Generic affinity setter function for MSI domains * @irq_data: The irq data associated to the interrupt @@ -89,13 +102,14 @@ int msi_domain_set_affinity(struct irq_data *irq_data, const struct cpumask *mask, bool force) { struct irq_data *parent = irq_data->parent_data; - struct msi_msg msg; + struct msi_msg msg[2] = { [1] = { }, }; int ret; ret = parent->chip->irq_set_affinity(parent, mask, force); if (ret >= 0 && ret != IRQ_SET_MASK_OK_DONE) { - BUG_ON(irq_chip_compose_msi_msg(irq_data, &msg)); - irq_chip_write_msi_msg(irq_data, &msg); + BUG_ON(irq_chip_compose_msi_msg(irq_data, msg)); + msi_check_level(irq_data->domain, msg); + irq_chip_write_msi_msg(irq_data, msg); } return ret; @@ -104,20 +118,21 @@ int msi_domain_set_affinity(struct irq_data *irq_data, static int msi_domain_activate(struct irq_domain *domain, struct irq_data *irq_data, bool early) { - struct msi_msg msg; + struct msi_msg msg[2] = { [1] = { }, }; - BUG_ON(irq_chip_compose_msi_msg(irq_data, &msg)); - irq_chip_write_msi_msg(irq_data, &msg); + BUG_ON(irq_chip_compose_msi_msg(irq_data, msg)); + msi_check_level(irq_data->domain, msg); + irq_chip_write_msi_msg(irq_data, msg); return 0; } static void msi_domain_deactivate(struct irq_domain *domain, struct irq_data *irq_data) { - struct msi_msg msg; + struct msi_msg msg[2]; - memset(&msg, 0, sizeof(msg)); - irq_chip_write_msi_msg(irq_data, &msg); + memset(msg, 0, sizeof(msg)); + irq_chip_write_msi_msg(irq_data, msg); } static int msi_domain_alloc(struct irq_domain *domain, unsigned int virq,