Re: [PATCH v2 2/5] iommu/arm-smmu: Convert to a global static identity domain

From: Jason Gunthorpe <jgg@nvidia.com>
To: Will Deacon <will@kernel.org>
Cc: iommu@lists.linux.dev, Joerg Roedel <joro@8bytes.org>,
	linux-arm-kernel@lists.infradead.org,
	Robin Murphy <robin.murphy@arm.com>,
	Nicolin Chen <nicolinc@nvidia.com>
Subject: Re: [PATCH v2 2/5] iommu/arm-smmu: Convert to a global static identity domain
Date: Tue, 12 Dec 2023 10:15:16 -0400	[thread overview]
Message-ID: <20231212141516.GE3014157@nvidia.com> (raw)
In-Reply-To: <20231212132708.GB29569@willie-the-truck>

On Tue, Dec 12, 2023 at 01:27:08PM +0000, Will Deacon wrote:
> > +static int arm_smmu_attach_dev_identity(struct iommu_domain *domain,
> > +					struct device *dev)
> > +{
> > +	struct arm_smmu_master_cfg *cfg = dev_iommu_priv_get(dev);
> > +	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > +	struct arm_smmu_device *smmu;
> > +	int ret;
> > +
> > +	if (!cfg)
> > +		return -ENODEV;
> > +	smmu = cfg->smmu;
> > +
> > +	ret = arm_smmu_rpm_get(smmu);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	arm_smmu_master_install_s2crs(cfg, S2CR_TYPE_BYPASS, 0, fwspec);
> > +
> > +	pm_runtime_set_autosuspend_delay(smmu->dev, 20);
> > +	pm_runtime_use_autosuspend(smmu->dev);
> 
> This is cargo-culted from arm_smmu_attach_dev() with the comments dropped
> and it's not clear at all to me that the autosuspend delay makes any sense
> for the identity domain.

Indeed, however it was how it worked before this split up.

> So I think it would be better to either drop the call to
> pm_runtime_set_autosuspend_delay() 

I looked through it more carefully and this does seem like the right
thing, so I will drop them.

Thanks,
Jason