On Wed, Jan 18, 2023 at 08:35:50PM -0500, Tianfei Zhang wrote: > This patchset introduces the FPGA hotplug manager (fpgahp) driver which > has been verified on the Intel N3000 card. > > When a PCIe-based FPGA card is reprogrammed, it temporarily disappears > from the PCIe bus. This needs to be managed to avoid PCIe errors and to > reprobe the device after reprogramming. > > To change the FPGA image, the kernel burns a new image into the flash on > the card, and then triggers the card BMC to load the new image into FPGA. > A new FPGA hotplug manager driver is introduced that leverages the PCIe > hotplug framework to trigger and manage the update of the FPGA image, > including the disappearance and reappearance of the card on the PCIe bus. > The fpgahp driver uses APIs from the pciehp driver. Two new operation > callbacks are defined in hotplug_slot_ops: > > - available_images: Optional: available FPGA images > - image_load: Optional: trigger the FPGA to load a new image > > > The process of reprogramming an FPGA card begins by removing all devices > associated with the card that are not required for the reprogramming of > the card. This includes PCIe devices (PFs and VFs) associated with the > card as well as any other types of devices (platform, etc.) defined within > the FPGA. The remaining devices are referred to here as "reserved" devices. > After triggering the update of the FPGA card, the reserved devices are also > removed. > > The complete process for reprogramming the FPGA are: > 1. remove all PFs and VFs except for PF0 (reserved). > 2. remove all non-reserved devices of PF0. > 3. trigger FPGA card to do the image update. > 4. disable the link of the hotplug bridge. > 5. remove all reserved devices under hotplug bridge. > 6. wait for image reload done via BMC, e.g. 10s. > 7. re-enable the link of hotplug bridge > 8. enumerate PCI devices below the hotplug bridge > > usage example: > [root@localhost]# cd /sys/bus/pci/slot/X-X/ > > Get the available images. > [root@localhost 2-1]# cat available_images > bmc_factory bmc_user retimer_fw > > Load the request images for FPGA Card, for example load the BMC user image: > [root@localhost 2-1]# echo bmc_user > image_load Why is all of this tied into the pci hotplug code? Shouldn't it be specific to this one driver instead? pci hotplug is for removing/adding PCI devices to the system, not messing with FPGA images. This feels like an abuse of the pci hotplug bus to me as this is NOT really a PCI hotplug bus at all, right? Or is it? If so, then the slots should show up under the PCI device itself, not in /sys/bus/pci/slot/. That location is there for old old stuff, we probably should move it one of these days as there's lots of special-cases in the driver core just because of that :( thanks, greg k-h
