linux-kernel - Re: [patch 33/37] iommu/arm-smmu-v3: Use msi_get

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Message-ID: <20211129105506.GA22761@willie-the-truck>
Date:   Mon, 29 Nov 2021 10:55:07 +0000
From:   Will Deacon <will@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        iommu@...ts.linux-foundation.org, dmaengine@...r.kernel.org,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
        Vinod Koul <vkoul@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sinan Kaya <okaya@...nel.org>
Subject: Re: [patch 33/37] iommu/arm-smmu-v3: Use msi_get_virq()

Hi Thomas,

On Sat, Nov 27, 2021 at 02:20:59AM +0100, Thomas Gleixner wrote:
> Let the core code fiddle with the MSI descriptor retrieval.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c |   19 +++----------------
>  1 file changed, 3 insertions(+), 16 deletions(-)
> 
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -3154,7 +3154,6 @@ static void arm_smmu_write_msi_msg(struc
>  
>  static void arm_smmu_setup_msis(struct arm_smmu_device *smmu)
>  {
> -	struct msi_desc *desc;
>  	int ret, nvec = ARM_SMMU_MAX_MSIS;
>  	struct device *dev = smmu->dev;
>  
> @@ -3182,21 +3181,9 @@ static void arm_smmu_setup_msis(struct a
>  		return;
>  	}
>  
> -	for_each_msi_entry(desc, dev) {
> -		switch (desc->msi_index) {
> -		case EVTQ_MSI_INDEX:
> -			smmu->evtq.q.irq = desc->irq;
> -			break;
> -		case GERROR_MSI_INDEX:
> -			smmu->gerr_irq = desc->irq;
> -			break;
> -		case PRIQ_MSI_INDEX:
> -			smmu->priq.q.irq = desc->irq;
> -			break;
> -		default:	/* Unknown */
> -			continue;
> -		}
> -	}
> +	smmu->evtq.q.irq = msi_get_virq(dev, EVTQ_MSI_INDEX);
> +	smmu->gerr_irq = msi_get_virq(dev, GERROR_MSI_INDEX);
> +	smmu->priq.q.irq = msi_get_virq(dev, PRIQ_MSI_INDEX);

Prviously, if retrieval of the MSI failed then we'd fall back to wired
interrupts. Now, I think we'll clobber the interrupt with 0 instead. Can
we make the assignments to smmu->*irq here conditional on the MSI being
valid, please?

Cheers,

Will