Re: [PATCH V8 01/11] iommu/of: Refactor of_iommu_configure() for error handling

[Jean-Philippe Brucker <jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org>]

Hello,

On 03/02/17 15:48, Sricharan R wrote:
> From: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
> 
> In preparation for some upcoming cleverness, rework the control flow in
> of_iommu_configure() to minimise duplication and improve the propogation
> of errors. It's also as good a time as any to switch over from the
> now-just-a-compatibility-wrapper of_iommu_get_ops() to using the generic
> IOMMU instance interface directly.
> 
> Tested-by: Marek Szyprowski <m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
> ---
>  [*] Resolved a conflict while rebasing on top linux-next as the patch
>      is not there in mainline master.
> 
>         "iommu: Drop the of_iommu_{set/get}_ops() interface"
>         https://lkml.org/lkml/2017/1/3/489
> 
>  drivers/iommu/of_iommu.c | 83 +++++++++++++++++++++++++++++++-----------------
>  1 file changed, 53 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index d7f480a..ee49081 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -96,6 +96,28 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index,
>  }
>  EXPORT_SYMBOL_GPL(of_get_dma_window);
>  
> +static const struct iommu_ops
> +*of_iommu_xlate(struct device *dev, struct of_phandle_args *iommu_spec)
> +{
> +	const struct iommu_ops *ops;
> +	struct fwnode_handle *fwnode = &iommu_spec->np->fwnode;
> +	int err;
> +
> +	ops = iommu_get_instance(fwnode);
> +	if (!ops || !ops->of_xlate)
> +		return NULL;
> +
> +	err = iommu_fwspec_init(dev, &iommu_spec->np->fwnode, ops);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	err = ops->of_xlate(dev, iommu_spec);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	return ops;
> +}
> +
>  static int __get_pci_rid(struct pci_dev *pdev, u16 alias, void *data)
>  {
>  	struct of_phandle_args *iommu_spec = data;
> @@ -105,10 +127,11 @@ static int __get_pci_rid(struct pci_dev *pdev, u16 alias, void *data)
>  }
>  
>  static const struct iommu_ops
> -*of_pci_iommu_configure(struct pci_dev *pdev, struct device_node *bridge_np)
> +*of_pci_iommu_init(struct pci_dev *pdev, struct device_node *bridge_np)
>  {
>  	const struct iommu_ops *ops;
>  	struct of_phandle_args iommu_spec;
> +	int err;
>  
>  	/*
>  	 * Start by tracing the RID alias down the PCI topology as
> @@ -123,56 +146,56 @@ static int __get_pci_rid(struct pci_dev *pdev, u16 alias, void *data)
>  	 * bus into the system beyond, and which IOMMU it ends up at.
>  	 */
>  	iommu_spec.np = NULL;
> -	if (of_pci_map_rid(bridge_np, iommu_spec.args[0], "iommu-map",
> -			   "iommu-map-mask", &iommu_spec.np, iommu_spec.args))
> -		return NULL;
> +	err = of_pci_map_rid(bridge_np, iommu_spec.args[0], "iommu-map",
> +			     "iommu-map-mask", &iommu_spec.np,
> +			     iommu_spec.args);
> +	if (err)
> +		return ERR_PTR(err);

This change doesn't work with of_pci_map_rid when the PCI RC isn't behind
an IOMMU:

        map = of_get_property(np, map_name, &map_len);
        if (!map) {
                if (target)
                        return -ENODEV;
                /* Otherwise, no map implies no translation */
                *id_out = rid;
                return 0;
        }

Previously with no iommu-map, we returned -ENODEV but it was discarded by
of_pci_iommu_configure. Now it is propagated and the whole device probing
fails. Instead, maybe of_pci_map_rid should always return 0 if no
iommu-map, and the caller should check if *target is still NULL?

Thanks,
Jean-Philippe

>  
> -	ops = iommu_get_instance(&iommu_spec.np->fwnode);
> -	if (!ops || !ops->of_xlate ||
> -	    iommu_fwspec_init(&pdev->dev, &iommu_spec.np->fwnode, ops) ||
> -	    ops->of_xlate(&pdev->dev, &iommu_spec))
> -		ops = NULL;
> +	ops = of_iommu_xlate(&pdev->dev, &iommu_spec);
>  
>  	of_node_put(iommu_spec.np);
>  	return ops;
>  }
>  
> -const struct iommu_ops *of_iommu_configure(struct device *dev,
> -					   struct device_node *master_np)
> +static const struct iommu_ops
> +*of_platform_iommu_init(struct device *dev, struct device_node *np)
>  {
>  	struct of_phandle_args iommu_spec;
> -	struct device_node *np;
>  	const struct iommu_ops *ops = NULL;
>  	int idx = 0;
>  
> -	if (dev_is_pci(dev))
> -		return of_pci_iommu_configure(to_pci_dev(dev), master_np);
> -
>  	/*
>  	 * We don't currently walk up the tree looking for a parent IOMMU.
>  	 * See the `Notes:' section of
>  	 * Documentation/devicetree/bindings/iommu/iommu.txt
>  	 */
> -	while (!of_parse_phandle_with_args(master_np, "iommus",
> -					   "#iommu-cells", idx,
> -					   &iommu_spec)) {
> -		np = iommu_spec.np;
> -		ops = iommu_get_instance(&np->fwnode);
> -
> -		if (!ops || !ops->of_xlate ||
> -		    iommu_fwspec_init(dev, &np->fwnode, ops) ||
> -		    ops->of_xlate(dev, &iommu_spec))
> -			goto err_put_node;
> -
> -		of_node_put(np);
> +	while (!of_parse_phandle_with_args(np, "iommus", "#iommu-cells",
> +					   idx, &iommu_spec)) {
> +		ops = of_iommu_xlate(dev, &iommu_spec);
> +		of_node_put(iommu_spec.np);
>  		idx++;
> +		if (IS_ERR_OR_NULL(ops))
> +			break;
>  	}
>  
>  	return ops;
> +}
> +
> +const struct iommu_ops *of_iommu_configure(struct device *dev,
> +					   struct device_node *master_np)
> +{
> +	const struct iommu_ops *ops;
> +
> +	if (!master_np)
> +		return NULL;
> +
> +	if (dev_is_pci(dev))
> +		ops = of_pci_iommu_init(to_pci_dev(dev), master_np);
> +	else
> +		ops = of_platform_iommu_init(dev, master_np);
>  
> -err_put_node:
> -	of_node_put(np);
> -	return NULL;
> +	return IS_ERR(ops) ? NULL : ops;
>  }
>  
>  static int __init of_iommu_init(void)
>