linux-kernel - Re: [PATCH 4/5] iommu/tegra-smmu: Add PCI support

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Date:   Mon, 28 Sep 2020 09:55:45 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     joro@...tes.org, krzk@...nel.org, vdumpa@...dia.com,
        jonathanh@...dia.com, linux-tegra@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] iommu/tegra-smmu: Add PCI support

On Sat, Sep 26, 2020 at 01:07:18AM -0700, Nicolin Chen wrote:
> This patch simply adds support for PCI devices.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---
>  drivers/iommu/tegra-smmu.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> index 97a7185b4578..9dbc5d7183cc 100644
> --- a/drivers/iommu/tegra-smmu.c
> +++ b/drivers/iommu/tegra-smmu.c
> @@ -15,6 +15,7 @@
>  #include <linux/spinlock.h>
>  #include <linux/dma-iommu.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/pci.h>
>  
>  #include <soc/tegra/ahb.h>
>  #include <soc/tegra/mc.h>
> @@ -935,6 +936,7 @@ static struct iommu_group *tegra_smmu_device_group(struct device *dev)
>  	const struct tegra_smmu_group_soc *soc;
>  	struct tegra_smmu_group *group;
>  	int swgroup = fwspec->ids[0];
> +	bool pci = dev_is_pci(dev);
>  	struct iommu_group *grp;
>  
>  	/* Find group_soc associating with swgroup */
> @@ -961,7 +963,7 @@ static struct iommu_group *tegra_smmu_device_group(struct device *dev)
>  	group->smmu = smmu;
>  	group->soc = soc;
>  
> -	group->group = iommu_group_alloc();
> +	group->group = pci ? pci_device_group(dev) : iommu_group_alloc();
>  	if (IS_ERR(group->group)) {
>  		devm_kfree(smmu->dev, group);
>  		mutex_unlock(&smmu->lock);
> @@ -1180,6 +1182,19 @@ struct tegra_smmu *tegra_smmu_probe(struct device *dev,
>  		return ERR_PTR(err);
>  	}
>  
> +#ifdef CONFIG_PCI
> +	if (!iommu_present(&pci_bus_type)) {
> +		pci_request_acs();
> +		err = bus_set_iommu(&pci_bus_type, &tegra_smmu_ops);
> +		if (err < 0) {
> +			bus_set_iommu(&platform_bus_type, NULL);
> +			iommu_device_unregister(&smmu->iommu);
> +			iommu_device_sysfs_remove(&smmu->iommu);
> +			return ERR_PTR(err);

It might be worth factoring out the cleanup code now that there are
multiple failures from which we may need to clean up.

Also, it'd be great if somehow we could do this without the #ifdef,
but I guess since we're using the pci_bus_type global variable directly,
there isn't much we can do here?

Thierry

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