Messages in this thread | | | From | Oza Oza <> | Date | Tue, 28 Mar 2017 10:20:12 +0530 | Subject | Re: [RFC PATCH 3/3] of: fix node traversing in of_dma_get_range |
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please find my comments inline.
On Mon, Mar 27, 2017 at 8:15 PM, Robin Murphy <robin.murphy@arm.com> wrote: > Hi Rob, > > On 27/03/17 15:34, Rob Herring wrote: >> On Sat, Mar 25, 2017 at 12:31 AM, Oza Pawandeep <oza.oza@broadcom.com> wrote: >>> it jumps to the parent node without examining the child node. >>> also with that, it throws "no dma-ranges found for node" >>> for pci dma-ranges. >>> >>> this patch fixes device node traversing for dma-ranges. >> >> What's the DT look like that doesn't work? > > The problem is the bodge in pci_dma_configure() where we don't have an > OF node for the actual device itself, so pass in the host bridge's OF > node instead. This happens to work well enough for dma-coherent, but I > don't think dma-ranges was even considered at the time. > > As it happens I'm currently halfway through writing an experiment > wherein pci_dma_configure() creates a temporary child node for the > of_dma_configure() call if no other suitable alternative (e.g. some > intermediate bridge node) exists. How hard are you likely to NAK that > approach? ;) > >> dma-ranges is supposed to be a bus property, not a device's property. >> So looking at the parent is correct behavior generally. > > Indeed, this patch as-is will break currently correct DTs (because we > won't find dma-ranges on the device, so will bail before even looking at > the parent as we should).
current parsing of dma-ranges assume that dma-ranges always to be found in parent node.
based on that, my thinking is following: couple of options
1) instead while(1) some meaningful condition such as while(!node) the following bail out is not required. if (!ranges) break;
2) have check based on dt-property to distinguish between pci and handle dma-ranges root bridge
but again these changes do not solve the entire problem for choosing right dma_mask. neither it actually correctly address root bridge pci dma-ranges.
and hence I have written https://lkml.org/lkml/2017/3/27/540
my final take is: this function does not need to change, let it parse memory mapped dma-ranges as it is doing.
I am more inclined to have generic pci dma-ranges and parsing. which following already addresses. https://lkml.org/lkml/2017/3/27/540
Regards, Oza.
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