Re: Handling MSI-X interrupts in the head stage for x86 platform
On 02.06.20 08:40, Alexander Frolov via Xenomai wrote: > > > On 6/1/20 12:23 PM, Meng, Fino via Xenomai wrote: >> >>> Sent: Monday, June 1, 2020 4:09 PM >>> >>> Hi all! >>> >>> I have a PCIe device in x86 motherboard that generate periodic MSI-X >>> interrupts and I would like to handle them in the head >>> stage, how it can be done? >>> Thank you! Appreciate any help! >>> >>> Best, >>> Alex >> Hi Alex, >> >> Kernel/driver/serial/16550A.c is a pci device, and have less code than >> net/igb driver, >> Which specific device u want to enable? Does it have a vanilla kernel >> driver already? > > Not sure that 16550A uses MSI-X interrupts. However, net/igb does. Is it > only driver in Xenomai that supports MSI-X? > > > I am using FPGA based device for periodic interrupts which is totally > custom. We have are own driver. > > Nevertheless, I have tested its latency from root stage driver and it is > appropriately good (not over than 60us). It seems that > msix irqs are not stalled anywhere. Is it possible? > > Can I guarantee that there will be no condition when MSIX interrupt will > be deferred by head stage on more than that? What latency > improvement I can expect from moving to RTDM based driver? > Head stage defers according to priorities: There there is an interrupt or a task for head stage pending, that will win. No guarantees beyond what your own workload can guarantee. In addition, no guarantees architecturally on what will happen in Linux (root stage) which could defer your interrupt. If you want determinism, move it to head stage. Jan PS: MSI-X works as well as MSI or legacy INTx. -- Siemens AG, Corporate Technology, CT RDA IOT SES-DE Corporate Competence Center Embedded Linux
Re: Handling MSI-X interrupts in the head stage for x86 platform
On 6/1/20 12:23 PM, Meng, Fino via Xenomai wrote: Sent: Monday, June 1, 2020 4:09 PM Hi all! I have a PCIe device in x86 motherboard that generate periodic MSI-X interrupts and I would like to handle them in the head stage, how it can be done? Thank you! Appreciate any help! Best, Alex Hi Alex, Kernel/driver/serial/16550A.c is a pci device, and have less code than net/igb driver, Which specific device u want to enable? Does it have a vanilla kernel driver already? Not sure that 16550A uses MSI-X interrupts. However, net/igb does. Is it only driver in Xenomai that supports MSI-X? I am using FPGA based device for periodic interrupts which is totally custom. We have are own driver. Nevertheless, I have tested its latency from root stage driver and it is appropriately good (not over than 60us). It seems that msix irqs are not stalled anywhere. Is it possible? Can I guarantee that there will be no condition when MSIX interrupt will be deferred by head stage on more than that? What latency improvement I can expect from moving to RTDM based driver? Thank you!
RE: Handling MSI-X interrupts in the head stage for x86 platform
>Sent: Monday, June 1, 2020 4:09 PM > >Hi all! > >I have a PCIe device in x86 motherboard that generate periodic MSI-X >interrupts and I would like to handle them in the head >stage, how it can be done? >Thank you! Appreciate any help! > >Best, > Alex Hi Alex, Kernel/driver/serial/16550A.c is a pci device, and have less code than net/igb driver, Which specific device u want to enable? Does it have a vanilla kernel driver already? BR / Fino (孟祥夫) Intel – IOTG Developer Enabling
