On Wed, Sep 02, 2015 at 10:55:20AM +0100, Marc Zyngier wrote:
On 02/09/15 10:33, Qais Yousef wrote:
On 08/28/2015 03:22 PM, Thomas Gleixner wrote:
On Fri, 28 Aug 2015, Qais Yousef wrote:
Thanks a lot for the detailed explanation. I wasn't looking for a quick and dirty solution but my view of the problem is much simpler than yours so my idea of a solution would look quick and dirty. I have a better appreciation of the problem now and a way to approach it :-)
From DT point of view are we OK with this form then
coprocessor { interrupt-source = <&intc INT_SPEC COP_HWAFFINITY>; interrupt-sink = <&intc INT_SPEC CPU_HWAFFINITY>; }and if the root controller sends normal IPI as it sends normal device interrupts then interrupt-sink can be a standard interrupts property (like in my case)
coprocessor { interrupt-source = <&intc INT_SPEC COP_HWAFFINITY>; interrupts = <INT_SPEC>; }Does this look right to you? Is there something else that needs to be covered still?
I'm not an DT wizard. I leave that to the DT experts.
Hi Marc Zyngier, Mark Rutland,
Any comments about the DT binding for the IPIs?
To recap, the proposal which is based on Marc Zyngier's is to use interrupt-source to represent an IPI from Linux CPU to a coprocessor and interrupt-sink to receive an IPI from coprocessor to Linux CPU. Hopefully the description above is self explanatory. Please let me know if you need more info. Thomas covered the routing, synthesising, and requesting parts in the core code. The remaining (high level) issue is how to describe the IPIs in DT.
I'm definitely *not* a DT expert! ;-) My initial binding proposal was only for wired interrupts, not for IPIs. There is definitely some common aspects, except for one part:
Who decides on the IPI number? So far, we've avoided encoding IPI numbers in the DT just like we don't encode MSIs, because they are programmable things. My feeling is that we shouldn't put the IPI number in the DT because the rest of the kernel uses them as well and could decide to use this particular IPI number for its own use: *clash*.
Agree. The best way I've found to design DT bindings is to imagine providing the DT to something other than Linux. The DT should *only* be describing the hardware. As such, I think we should be describing the connection here, and leaving the assignment up to the OS.
thx,
Jason.