From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mitchel Humpherys Subject: Re: [PATCH] iommu/arm-smmu: use a threaded handler for context interrupts Date: Fri, 23 Jan 2015 14:33:20 -0800 Message-ID: References: <1421970482-11722-1-git-send-email-mitchelh@codeaurora.org> <20150123112415.GD23058@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150123112415.GD23058-5wv7dgnIgG8@public.gmane.org> (Will Deacon's message of "Fri, 23 Jan 2015 11:24:15 +0000") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Will Deacon Cc: "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: iommu@lists.linux-foundation.org On Fri, Jan 23 2015 at 03:24:15 AM, Will Deacon wrote: > Hi Mitch, > > 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. -Mitch -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project