Messages in this thread | | | From | "Wu, Hao" <> | Subject | RE: [PATCH RFC] fpga: add FPGA Bus device framework | Date | Mon, 14 Aug 2017 12:59:19 +0000 |
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> On Tue, Aug 8, 2017 at 1:25 PM, Wu, Hao <hao.wu@intel.com> wrote: > >> On Thu, Aug 3, 2017 at 2:53 AM, Wu Hao <hao.wu@intel.com> wrote: > >> > On Wed, Aug 02, 2017 at 04:16:32PM -0500, Alan Tull wrote: > >> >> On Wed, Aug 2, 2017 at 7:19 AM, Wu Hao <hao.wu@intel.com> wrote: > >> >> > This patch is a RFC patch which replaces the patch[1] which > >> >> > creates 'fpga-dev' class as container device. It introduces > >> >> > a 'fpga' bus type, and provides interfaces to create/destroy > >> >> > fpga bus devices. This fpga bus device only could be used as > >> >> > a container device, and no drivers needed for it. > >> >> > > >> >> > There is no interface change, so this patch could be used > >> >> > together with other patches of the original patch set[2]. > >> >> > > >> >> > >> >> I am wondering whether this could be added to fpga-bridge.c so that > >> >> fpga-bridge becomes the fpga bus and fpga bus devices are under it. > >> >> The reasons for doing this are discussed in the other thread. > >> >> > >> >> > This following APIs are provided by FPGA Bus device framework: > >> >> > * fpga_dev_create > >> >> > Create fpga bus device under the given parent device. > >> >> > * fpga_dev_destroy > >> >> > Destroy fpga bus device > >> >> > >> >> This is being used in such that each fpga-dev is a container for > >> >> platform devices rather than fpga devices. That's not what I was > >> >> expecting. :) > >> > > >> > Hi Alan > >> > > >> > So does that mean in Intel FPGA PCIe driver, it needs to create > >> > a fpga-bridge (as base bridge?), > >> > >> Yes > >> > >> > and this fpga-bridge should register > >> > a fpga-bus and have a fpga bus device as its child, after that we can > >> > use this fpga bus device as container device, > >> > >> Could the bus code be added to fpga-bridge? Then the base bridge is > >> the container device. A fpga-region would be under that and the AFU > >> and FME fpga devices would be under it. > >> > >> > and create sub feature > >> > devices (e.g AFU and FME platform device) > >> > >> We're talking about adding a new bus to the kernel here, not platform bus. > >> > >> > under it, and user application > >> > could locate it in /sys/bus/fpga/devices/. Is my understanding correct? :) > >> > >> So sysfs may end up something like this in your case: > >> > >> /sys/bus/fpga/devices/fpga.0/intel-fpga-fme.0 > >> /sys/bus/fpga/devices/fpga.0/intel-fpga-port.0 > >> /sys/bus/fpga/devices/fpga.0/intel-fpga-port.1 > >> /sys/bus/fpga/devices/fpga.0/fpga-mgr0 > >> /sys/bus/fpga/devices/fpga.0/fpga-br1 > >> /sys/bus/fpga/devices/fpga.0/fpga-br2 > > > > Hi Alan > > > > I am a little confused on this. > > > > It seems that we could not have multiple fpga-br/region/mgr under one device. > > As in patch set2, intel-fpga-fme.0 creates platform devices as children, and > register > > fpga-bridges/regions/mgr under these children platform devices. This is why 3 > new > > platform device driver introduced in this patch set 2 to match with those new > created > > children platform devices. > > > > So it is something like this > > /sys/bus/fpga/devices/fpga.0/intel-fpga-fme.0/intel-fpga-fme- > region.0/fpga_region/region0 > > /sys/bus/fpga/devices/fpga.0/intel-fpga-fme.0/intel-fpga-fme- > region.1/fpga_region/region1 > > /sys/bus/fpga/devices/fpga.0/intel-fpga-fme.0/intel-fpga-fme- > br.0/fpga_bridge/br1 > > /sys/bus/fpga/devices/fpga.0/intel-fpga-fme.0/intel-fpga-fme- > br.1/fpga_region/br2 > > /sys/bus/fpga/devices/fpga.1 > > /sys/bus/fpga/devices/fpga.2 > > Hi Hao, > > OK I see that now. Because the regions, mgr, and bridges are all > children of the fme's. > > > > > br0 should be the base bridge. fpga.1 and 2 are the child fpga bus device of > fpga bridge. > > > >> > >> /sys/bus/fpga/devices/fpga.1/fpga-region1 > >> /sys/bus/fpga/devices/fpga.2/fpga-region2 > >> > >> /sys/bus/fpga/devices/fpga.3/intel-fpga-fme.1 > >> /sys/bus/fpga/devices/fpga.3/intel-fpga-port.2 > >> /sys/bus/fpga/devices/fpga.3/intel-fpga-port.3 > >> /sys/bus/fpga/devices/fpga.0/fpga-mgr1 > >> /sys/bus/fpga/devices/fpga.3/fpga-br4 > >> /sys/bus/fpga/devices/fpga.3/fpga-br5 > >> > >> /sys/bus/fpga/devices/fpga.4/fpga-region4 > >> /sys/bus/fpga/devices/fpga.5/fpga-region5 > >> > >> fpga-br0 and 3 are base bridges (on top of PCIe) which show up as > >> fpga.0 and 3. Regions 0 and 3 are base regions. > >> > >> fpga.0 and fpga.3 correspond to the real FPGA devices. > >> > >> > > >> > And if we have second level fpga-bridge for PR regions, then they > >> > should register fpga-bus and fpga bus type device as child too? > >> > If yes, then we need a method for user application to distinguish > >> > which one represents the FPGA device in /sys/bus/fpga/devices/, right? > >> > >> To find a bus that is a fpga, userspace only needs to look for busses > >> that have an FME (or a mgr). > > > > Do you mean that check all fpga-dev.x folder to see if anyone has FME? > > > > Then it is still not friendly to user space, as we may have a lot of bridges > > (and regions) on one system. > > It doesn't sound too hard for userspace code to go through sysfs once > and find the FME's. > > > > > And looks like no big difference that we reuse base fpga-region as > > container. Search all regionx in /sys/class/fpga_region/ to see if anyone > > has a FME. > > > > How do you think? : ) > > Yes, looking for > /sys/class/fpga_region/region*/device/intel-fpga-fme.* That's not so > bad, right? :) > > Then the fpga-dev stuff can go away and we can stop worrying about all > the issues involved in implementing a fpga bus or class.
Hi Alan
Thanks for your feedback.
I think the only concern here is I'm not sure if we will have some fpga devices with a large number fpga regions (e.g 100+) in the future. If there are many regions in the system, then the enduser / application needs to search all the regions one by one, which seems not perfect.
Hao
> > Alan > > > > > Hao > > > >> > >> > It seems to be a similar case that we see a lot of regions in > >> > /sys/class/fpga_region/ but not sure which one is the base region. :) > >> > >> I understand that the goal of fpga-dev was to describe the topology > >> (which is the function of a bus, not a class as Rob explained). To be > >> honest, I'm still pondering the implications of adding a fpga bus. > >> > >> Alan
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