Hi Yijing > -----Original Message----- > From: linux-pci-owner@xxxxxxxxxxxxxxx [mailto:linux-pci-owner@xxxxxxxxxxxxxxx] > On Behalf Of Yijing Wang > Sent: Monday, August 04, 2014 8:34 AM > To: Basu Arnab-B45036 > Cc: Xinwei Hu; Wuyun; Bjorn Helgaas; linux-pci@xxxxxxxxxxxxxxx; > Paul.Mundt@xxxxxxxxxx; James E.J. Bottomley; Marc Zyngier; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; Russell King; linux-arch@xxxxxxxxxxxxxxx; > virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; Hanjun Guo; linux- > kernel@xxxxxxxxxxxxxxx > Subject: Re: [RFC PATCH 00/11] Refactor MSI to support Non-PCI device > > >> MSI was introduced in PCI Spec 2.2. Currently, kernel MSI driver > >> codes are bonding with PCI device. Because MSI has a lot advantages in > design. > >> More and more non-PCI devices want to use MSI as their default interrupt. > >> The existing MSI device include HPET. HPET driver provide its own MSI > >> code to initialize and process MSI interrupts. In the latest GIC v3 > >> spec, legacy device can deliver MSI by the help of a relay device > >> named consolidator. > >> Consolidator can translate the legacy interrupts connected to it to > >> MSI/MSI-X. And new non-PCI device will be designed to support MSI in > >> future. So make the MSI driver code be generic will help the non-PCI > >> device use MSI more simply. > > > > As per my understanding the GICv3 provides a service that will convert writes > to a specified address to IRQs delivered to the core and as you mention above > MSIs are part of the PCI spec. So I can see a strong case for non-PCI devices to > want MSI like functionality without being fully compliant with the requirements > of the MSI spec. > > In GICv3, MBI is named for the service, but there is no more detailed > information about it, only we can know is MBI is analogous to MSI, MBI devices > must have address/data registers, but other registers like enable/mask/ctrl are > not mandatory requirement. > I don't know whether the MBI spec will be release, but anyway I think MSI > refactoring is make sense, there are some existing Non-PCI MSI device like hpet, > dmar. > For simplicity, let name MSI and MBI to MSI temporarily. > > > > My question is do we necessarily want to rework so much of the PCI-MSI layer > to support non PCI devices? Or will it be sufficient to create a framework to > allow non PCI devices to hook up with a device that can convert their writes to > an IRQ to the core. > > > > As I understand it, the msi_chip is (almost) such a framework. The only > problem being that it makes some PCI specific assumptions (such as PCI specific > writes from within msi_chip functions). Won't it be sufficient to make the > msi_chip framework generic enough to be used by non-PCI devices and let each > bus/device manage any additional requirements (such as configuration flow, bit > definitions etc) that it places on message based interrupts? > > msi_chip framework is important to support that, but I think maybe it's not > enough, msi_chip is only responsible for IRQ allocation, teardown, etc.. > > The key difference between PCI device and Non-PCI MSI is the interfaces to > access hardware MSI registers. > for instance, currently, msi_chip->setup_irq() to setup MSI irq and configure > the MSI address/data registers, so we need to provide device specific > write_msi_msg() interface, then when we call msi_chip->setup_irq(), the device > MSI registers can be configured appropriately. What if we can register/override the setup_irq() from bus-driver (not sure, but may be device-driver itself). Example PCI bus-driver will provide setup_irq() (or the part of setup_irq which set address and data in h/w) by PCI bus, which configure address/data in h/w as per PCI standard. We in Freescale will be using MSI for the devices behind a new-bus (which is not PCI based), We have a separate bus driver for same. And this new bus driver register/provide its own address/data write function which is based on that specific bus protocol. Thanks -Bharat > > My patchset is just a RFC draft, I will update it later, all we want to do is > make kernel support Non-PCI MSI devices. > > Thanks! > Yijing. > > > > > > Thanks > > Arnab > > -- > > To unsubscribe from this list: send the line "unsubscribe > > linux-kernel" in the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > > > . > > > > > -- > Thanks! > Yijing > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body > of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
