Re: [PATCH v2 4/7] iommu/of: Handle iommu-map property for PCI

[Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>]

On 14/06/16 15:45, Will Deacon wrote:
> On Fri, Jun 03, 2016 at 06:15:39PM +0100, Robin Murphy wrote:
>> Now that we have a way to pick up the RID translation and target IOMMU,
>> hook up of_iommu_configure() to bring PCI devices into the of_xlate
>> mechanism and allow them IOMMU-backed DMA ops without the need for
>> driver-specific handling.
>>
>> CC: Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
>> CC: Frank Rowand <frowand.list-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
>> ---
>>
>> v2: Skip disabled IOMMUs.
>>
>>   drivers/iommu/of_iommu.c | 44 +++++++++++++++++++++++++++++++++++++-------
>>   1 file changed, 37 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
>> index 662f9a600f4f..5716131199b3 100644
>> --- a/drivers/iommu/of_iommu.c
>> +++ b/drivers/iommu/of_iommu.c
>> @@ -22,6 +22,7 @@
>>   #include <linux/limits.h>
>>   #include <linux/of.h>
>>   #include <linux/of_iommu.h>
>> +#include <linux/of_pci.h>
>>   #include <linux/slab.h>
>>
>>   static const struct of_device_id __iommu_of_table_sentinel
>> @@ -134,20 +135,49 @@ const struct iommu_ops *of_iommu_get_ops(struct device_node *np)
>>   	return ops;
>>   }
>>
>> +static int __get_pci_rid(struct pci_dev *pdev, u16 alias, void *data)
>> +{
>> +	struct of_phandle_args *iommu_spec = data;
>> +
>> +	iommu_spec->args[0] = alias;
>> +	return iommu_spec->np == pdev->bus->dev.of_node;
>> +}
>> +
>>   const struct iommu_ops *of_iommu_configure(struct device *dev,
>>   					   struct device_node *master_np)
>>   {
>>   	struct of_phandle_args iommu_spec;
>> -	struct device_node *np;
>> +	struct device_node *np = NULL;
>>   	const struct iommu_ops *ops = NULL;
>>   	int idx;
>>
>> -	/*
>> -	 * We can't do much for PCI devices without knowing how
>> -	 * device IDs are wired up from the PCI bus to the IOMMU.
>> -	 */
>> -	if (dev_is_pci(dev))
>> -		return NULL;
>> +	if (dev_is_pci(dev)) {
>> +		/*
>> +		 * Start by tracing the RID alias down the PCI topology as
>> +		 * far as the host bridge whose OF node we have...
>> +		 */
>> +		iommu_spec.np = master_np;
>> +		pci_for_each_dma_alias(to_pci_dev(dev), __get_pci_rid,
>> +				       &iommu_spec);
>> +		/*
>> +		 * ...then find out what that becomes once it escapes the PCI
>> +		 * bus into the system beyond, and which IOMMU it ends up at.
>> +		 */
>> +		if (of_pci_map_rid(master_np, "iommu-map", iommu_spec.args[0],
>> +				   &np, iommu_spec.args) ||
>> +		    !of_device_is_available(np))
>> +			return NULL;
>
> Hmm, do we need to of_node_put(np) in the case that it's not available?

Ah yes, now I see; I moved the put into the loop iteration for the 
non-PCI case so that a "continue" does the job, but I've not handled the 
equivalent here.

Robin.

>
> Will
>