On Monday 07 July 2014, Liviu Dudau wrote:
On Sat, Jul 05, 2014 at 09:46:09PM +0100, Arnd Bergmann wrote:
On Saturday 05 July 2014 14:25:52 Rob Herring wrote:
On Tue, Jul 1, 2014 at 1:43 PM, Liviu Dudau Liviu.Dudau@arm.com wrote:
The ranges property for a host bridge controller in DT describes the mapping between the PCI bus address and the CPU physical address. The resources framework however expects that the IO resources start at a pseudo "port" address 0 (zero) and have a maximum size of IO_SPACE_LIMIT. The conversion from pci ranges to resources failed to take that into account.
I don't think this change is right. There are 2 resources: the PCI bus addresses and cpu addresses. This function deals with the cpu addresses. Returning pci addresses for i/o and cpu addresses for memory is going to be error prone. We probably need both cpu and pci resources exposed to host controllers.
Making the new function only deal with i/o bus resources and naming it of_pci_range_to_io_resource would be better.
I think you are correct that this change by itself is will break existing drivers that rely on the current behavior of of_pci_range_to_resource, but there is also something wrong with the existing implementation:
Either I'm very confused or I've managed to confuse everyone else. The I/O resources described using CPU addresses *are* using "pseudo" port based addresses (or at least that is my understanding and my reading of the code). Can you point me to a function that is expecting the IO resource to have the start address at the physical address of the mapped space?
pci_v3_preinit() in arch/arm/mach-integrator/pci_v3.c for instance takes the resource returned by of_pci_range_to_resource and programs the start and size into hardware registers that expect a physical address as far as I can tell.
I was trying to fix exactly this issue, that you cannot use the resource structure returned by this function in any call that is expecting an IO resource.
I looked at the other drivers briefly, and I think you indeed fix the Tegra driver with this but break the integrator driver as mentioned above. The other callers of of_pci_range_to_resource() are apparently not impacted as they recalculate the values they get.
Arnd