On Thu, 11 Feb 2016, atull wrote: > On Thu, 11 Feb 2016, Rob Herring wrote: > > > On Thu, Feb 11, 2016 at 2:49 PM, atull <atull@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > On Fri, 5 Feb 2016, atull@xxxxxxxxxxxxxxxxxxxxx wrote: > > > > > >> From: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx> > > >> > > >> v16 Refactors the FPGA Area and FPGA Bus into single thing called an > > >> FPGA Region and eliminates using simple-bus. I'm using the word > > >> "region" as it's a term is used in the literature of both the major > > >> FPGA manufacturors. > > >> > > >> Changes for v16: > > >> * Refactor the FPGA Area and FPGA Bus into a FPGA Region. > > >> * Don't use simple-bus. > > >> * FPGA Managers and FPGA Bridges are now specified by phandle using the > > >> "fpga-mgr" and "fpga-bridges" properties. fpga-bridges can specify > > >> more than one bridge. > > >> * Device Tree overlays should be targeted to a FPGA Region. > > >> * The overlays need only contain firmware-name and the child nodes. > > >> * To model a system containing >1 partial reconfiguration region, > > >> an overlay could add FPGA Regions to the base FPGA Regions. > > >> * Child FPGA Regions inherit the parent FGPA Manager, but specify > > >> their own set of bridges if needes as partial reconfig regions > > >> will likely need their own bridges. > > >> * All this is discussed in bindings/fpga/fpga-region.txt > > >> > > >> One other highlight: > > >> The little engine that runs this thing is a reconfig notifier > > >> in fpga-region.c. This notifier that will program an FPGA if a > > >> "firmware-name" property gets added to a fpga-region. Then > > >> it will call of_platform_populate(). The current behavior in Linux > > >> when a DT overlay is applied is that the reconfig notifications > > >> go out in heirarchical order: first notifications are for the > > >> properties, then notifications for the child nodes. So an overlay > > >> that adds a 'firmware-name' property and some child nodes to a > > >> fpga-region will cause FPGA programming and child node > > >> populating in the right order. > > > > > > I figured out how to get rid of the reconfig notifier. > > > > > >> > > >> One issue with the dynamic DT stuff: > > >> I've tried returning and error from the notifier if FPGA programming > > >> fails; the error is noted on the console, but the child nodes > > >> get probed anyway. > > > > > > I looked into it further and now I've got a solution for this issue > > > that I can post soon. I can stop using the DT overlay configfs > > > interface and add a sysfs file for applying an overlay to an FPGA > > > region. The FPGA region implementation will see the overlay before it > > > becomes part of the live tree. Then it can do the FPGA programming > > > and see that succeed before the child nodes become part of the live > > > tree. If FPGA programming fails, the overlay will be rejected before > > > it becomes part of the live tree. By the time 'firmware-name' and the > > > child nodes show up in the live tree, they will be post-configuration > > > information. > > > > Um, no. We don't need 2 interfaces for loading overlays from > > userspace. I could see this being a common problem and it needs to be > > solved. But given the configfs interface is not upstream yet, perhaps > > you should worry about that after the current series is in. > > > > Perhaps we need a pre-add notifier and the core will only load the > > overlay if nothing handles it. Really, a solution without notifiers > > would be preferred. Maybe register handlers with the DT core for > > certain paths. > > > > Rob > > > > Yes. If any handler returns error, the overlay doesn't go into the > main tree. Handler type to be registed could be: > > int pre_add_handler(struct device_node *overlay, > struct device_node *target) And a third parameter of some flags to indicate whether the overlay is being added or removed. > > That gives us the overlay after it's been unflattened and phandles > resolved and the node that it was targeted to. I was going to > need find_target_node() to be exported, but this avoids that. > > Registration could by compatible string, of match, or path. Path > would be too rigid in my case, I'd want to register for compatible > "fpga-region" > > Alan > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
