From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 28 Jan 2015 12:07:39 +0000 Subject: [PATCH] iommu/arm-smmu: use a threaded handler for context interrupts In-Reply-To: References: <1421970482-11722-1-git-send-email-mitchelh@codeaurora.org> <20150123112415.GD23058@arm.com> Message-ID: <20150128120738.GJ1569@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Jan 23, 2015 at 10:33:20PM +0000, Mitchel Humpherys wrote: > On Fri, Jan 23 2015 at 03:24:15 AM, Will Deacon wrote: > > On Thu, Jan 22, 2015 at 11:48:02PM +0000, Mitchel Humpherys wrote: > >> Context interrupts can call domain-specific handlers which might sleep. > >> Currently we register our handler with request_irq, so our handler is > >> called in atomic context, so domain handlers that sleep result in an > >> invalid context BUG. Fix this by using request_threaded_irq. > >> > >> This also prepares the way for doing things like enabling clocks within > >> our interrupt handler. > >> > >> Signed-off-by: Mitchel Humpherys > >> --- > >> drivers/iommu/arm-smmu.c | 5 +++-- > >> 1 file changed, 3 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > >> index 6cd47b75286f..81f6b54d94b1 100644 > >> --- a/drivers/iommu/arm-smmu.c > >> +++ b/drivers/iommu/arm-smmu.c > >> @@ -973,8 +973,9 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain, > >> spin_unlock_irqrestore(&smmu_domain->lock, flags); > >> > >> irq = smmu->irqs[smmu->num_global_irqs + cfg->irptndx]; > >> - ret = request_irq(irq, arm_smmu_context_fault, IRQF_SHARED, > >> - "arm-smmu-context-fault", domain); > >> + ret = request_threaded_irq(irq, NULL, arm_smmu_context_fault, > >> + IRQF_ONESHOT | IRQF_SHARED, > >> + "arm-smmu-context-fault", domain); > >> if (IS_ERR_VALUE(ret)) { > >> dev_err(smmu->dev, "failed to request context IRQ %d (%u)\n", > >> cfg->irptndx, irq); > > > > I think I'd rather keep a simple atomic handler, then have a threaded > > handler for actually issuing the report_iommu_fault. i.e. we only wake > > the thread when it looks like there's some work to do. That also works > > much better for shared interrupts. > > Are you still against adding clock support to the driver? If not, we'll > need to move to a threaded handler when clocks come in anyways... > > Can you elaborate what you mean regarding shared interrupts? Even > without clocks it seems like the code clarity / performance tradeoff > would favor a threaded handler, given that performance isn't important > here. With a shared handler (e.g. a bunch of context banks have the same IRQ) then I assume that we don't want to end up with multiple handler threads all tripping over each other. I'd rather have one thread that handles work queued up by multiple low-level handlers. Do you have a preference either way? Will