linux-kernel - Re: [PATCH v3 6/7] iommu/arm-smmu-v3: Add workaround for Cavium ThunderX2 erratum #126

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Message-ID: <a2618ab6-6609-7885-3b62-c1c1f170c318@arm.com>
Date:   Mon, 8 May 2017 12:21:28 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Geetha sowjanya <gakula@...iumnetworks.com>, will.deacon@....com,
        lorenzo.pieralisi@....com, hanjun.guo@...aro.org,
        sudeep.holla@....com, iommu@...ts.linux-foundation.org
Cc:     jcm@...hat.com, linux-kernel@...r.kernel.org,
        robert.richter@...ium.com, catalin.marinas@....com,
        sgoutham@...ium.com, linux-arm-kernel@...ts.infradead.org,
        linux-acpi@...r.kernel.org, geethasowjanya.akula@...il.com,
        linu.cherian@...ium.com,
        Geetha Sowjanya <geethasowjanya.akula@...ium.com>
Subject: Re: [PATCH v3 6/7] iommu/arm-smmu-v3: Add workaround for Cavium
 ThunderX2 erratum #126

On 05/05/17 13:08, Geetha sowjanya wrote:
> From: Geetha Sowjanya <geethasowjanya.akula@...ium.com>
> 
> Cavium ThunderX2 SMMU doesn't support MSI and also doesn't have unique irq
> lines for gerror, eventq and cmdq-sync.
> 
> This patch addresses the issue by checking if any interrupt sources are
> using same irq number, then they are registered as shared irqs.
> 
> Signed-off-by: Geetha Sowjanya <geethasowjanya.akula@...ium.com>
> ---
>  drivers/iommu/arm-smmu-v3.c | 32 ++++++++++++++++++++++++++++----
>  1 file changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 016b702..46428e7 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -2236,10 +2236,30 @@ static void arm_smmu_setup_msis(struct arm_smmu_device *smmu)
>  	devm_add_action(dev, arm_smmu_free_msis, dev);
>  }
>  
> +static int get_irq_flags(struct arm_smmu_device *smmu, int irq)
> +{
> +	int match_count = 0;
> +
> +	if (irq == smmu->evtq.q.irq)
> +		match_count++;
> +	if (irq == smmu->cmdq.q.irq)
> +		match_count++;
> +	if (irq == smmu->gerr_irq)
> +		match_count++;
> +	if (irq == smmu->priq.q.irq)
> +		match_count++;
> +
> +	if (match_count > 1)
> +		return IRQF_SHARED | IRQF_ONESHOT;
> +
> +	return 0;

I'd say just have this return IRQF_ONESHOT in the non-shared case...

> +}
> +
>  static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
>  {
>  	int ret, irq;
>  	u32 irqen_flags = IRQ_CTRL_EVTQ_IRQEN | IRQ_CTRL_GERROR_IRQEN;
> +	u32 irqflags = 0;
>  
>  	/* Disable IRQs first */
>  	ret = arm_smmu_write_reg_sync(smmu, 0, ARM_SMMU_IRQ_CTRL,
> @@ -2254,9 +2274,10 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
>  	/* Request interrupt lines */
>  	irq = smmu->evtq.q.irq;
>  	if (irq) {
> +		irqflags = get_irq_flags(smmu, irq);
>  		ret = devm_request_threaded_irq(smmu->dev, irq, NULL,
>  						arm_smmu_evtq_thread,
> -						IRQF_ONESHOT,
> +						IRQF_ONESHOT | irqflags,

...and pass get_irq_flags(smmu, irq) directly as the argument here.

The local variable and intermediate logic only seem to add unnecessary
complexity, given that the two cases we actually end up with are:

IRQF_ONESHOT | 0

vs.

IRQF_ONESHOT | IRQF_SHARED | IRQF_ONESHOT

neither of which looks particularly sensible.

Robin.

>  						"arm-smmu-v3-evtq", smmu);
>  		if (ret < 0)
>  			dev_warn(smmu->dev, "failed to enable evtq irq\n");
> @@ -2264,8 +2285,9 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
>  
>  	irq = smmu->cmdq.q.irq;
>  	if (irq) {
> +		irqflags = get_irq_flags(smmu, irq);
>  		ret = devm_request_irq(smmu->dev, irq,
> -				       arm_smmu_cmdq_sync_handler, 0,
> +				       arm_smmu_cmdq_sync_handler, irqflags,
>  				       "arm-smmu-v3-cmdq-sync", smmu);
>  		if (ret < 0)
>  			dev_warn(smmu->dev, "failed to enable cmdq-sync irq\n");
> @@ -2273,8 +2295,9 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
>  
>  	irq = smmu->gerr_irq;
>  	if (irq) {
> +		irqflags = get_irq_flags(smmu, irq);
>  		ret = devm_request_irq(smmu->dev, irq, arm_smmu_gerror_handler,
> -				       0, "arm-smmu-v3-gerror", smmu);
> +				       irqflags, "arm-smmu-v3-gerror", smmu);
>  		if (ret < 0)
>  			dev_warn(smmu->dev, "failed to enable gerror irq\n");
>  	}
> @@ -2282,9 +2305,10 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
>  	if (smmu->features & ARM_SMMU_FEAT_PRI) {
>  		irq = smmu->priq.q.irq;
>  		if (irq) {
> +			irqflags = get_irq_flags(smmu, irq);
>  			ret = devm_request_threaded_irq(smmu->dev, irq, NULL,
>  							arm_smmu_priq_thread,
> -							IRQF_ONESHOT,
> +							IRQF_ONESHOT | irqflags,
>  							"arm-smmu-v3-priq",
>  							smmu);
>  			if (ret < 0)
>