[RFC PATCH] ARM64: PCI: inherit root controller's dma-coherent

[Ming Lei]

On Thu, Nov 27, 2014 at 5:03 PM, Arnd Bergmann <arnd at arndb.de> wrote:
> On Thursday 27 November 2014 13:41:31 Ming Lei wrote:
>
>> @@ -37,6 +38,21 @@ resource_size_t pcibios_align_resource(void *data, const struct resource *res,
>>       return res->start;
>>  }
>>
>> +/* Inherit root controller's dma coherent ops */
>> +static void pci_dma_config(struct pci_dev *dev)
>> +{
>> +     struct pci_bus *bus = dev->bus;
>> +     struct device *host;
>> +
>> +     while (!pci_is_root_bus(bus)) {
>> +             bus = bus->parent;
>> +     }
>> +
>> +     host = bus->dev.parent->parent;
>> +     if (of_dma_is_coherent(host->of_node))
>> +             set_arch_dma_coherent_ops(&dev->dev);
>> +}
>> +
>
> I think we need something more generic than this: This is not architecture
> specific at all, and we have to deal with IOMMU, swiotlb, dma offset and
> dma mask as well, coherency is definitely not the only issue.

That may take a bit long since ARCHs, dma, and pci subsystem are
involved about the change.

Given ARM64 PCI and related host controller driver are merged
already, could this patch be applied to fix current problem first?


Thanks,
Ming Lei