On 2019/5/9 18:50, Liuyixian (Eason) wrote: > > > On 2019/5/2 21:03, Jason Gunthorpe wrote: >> On Tue, Apr 30, 2019 at 04:27:41PM +0800, Liuyixian (Eason) wrote: >>> >>> >>> On 2019/4/27 5:05, Leon Romanovsky wrote: >>>> On Fri, Apr 26, 2019 at 11:36:56AM -0300, Jason Gunthorpe wrote: >>>>> On Fri, Apr 26, 2019 at 06:12:11PM +0800, Liuyixian (Eason) wrote: >>>>> >>>>>> However, I have talked with our chip team about function clear >>>>>> functionality. We think it is necessary to inform the chip to >>>>>> perform the outstanding task and some cleanup work and restore >>>>>> hardware resources in time when rmmod ko. Otherwise, it is >>>>>> dangerous to reuse the hardware as it can not guarantee those >>>>>> work can be done well without the notification from our driver. >>>>> >>>>> If it is dangerous to reuse the hardware then you have to do this >>>>> cleanup on device startup, not on device removal. >>>> >>>> Right, I can think about gazillion ways to brick such HW. >>>> The simplest way will be to call SysRq during RDMA traffic >>>> and no cleanup function will be called in such case. >>>> >>>> Thanks >>> >>> Hi Jason and Leon, >>> >>> As hip08 is a fake pcie device, we could not disassociate and stop the hardware access >>> through the chain break mechanism as a real pcie device. Alternatively, function clear >>> is used as a notification to the hardware to stop accessing and ensure to not read or >>> write DDR later. That is, the role of function clear to hip08 is similar as the chain >>> break to pcie device. >> >> What? This hardware is broken and doesn't respond to the bus master >> enable bit in the PCI config space?? >> > Hi Jason, > > Sorry to reply to you late. > > Yes, the bus master enable bit should be set by a pcie device when startup and removal. > The hns (nic) module use it as well. However, we couldn't use/operate this bit in hip08 > as it shares the PF(physical function) with nic. Therefore, we need function clear to > notify the hardware to do the cleanup thing and cache write back. > > Thanks. > Hi Jason and Leon, Do you have further more suggestions? Thanks.
