Hi Jean, > -----Original Message----- > From: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com> > Sent: Friday, 10 May, 2019 07:07 PM > To: Pankaj Bansal <pankaj.ban...@nxp.com>; Will Deacon > <will.dea...@arm.com>; Robin Murphy <robin.mur...@arm.com>; Joerg > Roedel <j...@8bytes.org> > Cc: iommu@lists.linux-foundation.org; Varun Sethi <v.se...@nxp.com>; linux- > arm-ker...@lists.infradead.org; Nipun Gupta <nipun.gu...@nxp.com> > Subject: Re: [ARM SMMU] Dynamic StreamID allocation > > On 10/05/2019 13:33, Pankaj Bansal wrote: > > Hi Will/Robin/Joerg, > > > > I am s/w engineer from NXP India Pvt. Ltd. > > We are using SMMU-V3 in one of NXP SOC. > > I have a question about the SMMU Stream ID allocation in linux. > > > > Right now the Stream IDs allocated to a device are mapped via device tree to > the device. > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Felix > > ir.bootlin.com%2Flinux%2Flatest%2Fsource%2FDocumentation%2Fdevicetree% > > 2Fbindings%2Fiommu%2Farm%2Csmmu- > v3.txt%23L39&data=02%7C01%7Cpankaj > > .bansal%40nxp.com%7C3cbe8bd4827e425afd0f08d6d54c925e%7C686ea1d3b > c2b4c6 > > > fa92cd99c5c301635%7C0%7C0%7C636930922220665343&sdata=vIG5u5n > XR5iRp > > uuuGjeFxKBtA5f5ohf91znXX0QWm1c%3D&reserved=0 > > > > As the device tree is passed from bootloader to linux, we detect all the > > stream > IDs needed by a device in bootloader and add their IDs in respective device > nodes. > > For each PCIE Endpoint (a unique BDF (Bus Device Function)) on PCIE bus, we > are assigning a unique Stream ID in bootloader. > > > > However, this poses an issue with PCIE hot plug. > > If we plug in a pcie device while linux is running, a unique BDF is > > assigned to > the device, for which there is no stream ID in device tree. > > > > How can this problem be solved in linux? > > Assuming the streamID associated to a BDF is predictable (streamID = BDF > + constant), using the iommu-map property should just work: > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir.boo > tlin.com%2Flinux%2Flatest%2Fsource%2FDocumentation%2Fdevicetree%2Fbind > ings%2Fpci%2Fpci- > iommu.txt&data=02%7C01%7Cpankaj.bansal%40nxp.com%7C3cbe8bd482 > 7e425afd0f08d6d54c925e%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0 > %7C636930922220665343&sdata=GkkovEnvhd5dN%2BGdh%2FnKCyW5Cd > EnLDP3cWTrk%2B%2FO7EQ%3D&reserved=0 > > It describes the streamIDs of all possible BDFs, including hotplugged > functions.
You mean that we should increase the "length" parameter (in (rid-base,iommu,iommu-base,length) touple) ? This would cater to any *new* Bus Device Function being detected on PCIE bus? Is that right ? Right now when we make iommu-map in bootloader, we are giving one RID per BDF: https://elixir.bootlin.com/u-boot/latest/source/drivers/pci/pcie_layerscape_fixup.c#L168 But isn't the better approach to make it dynamic in linux? i.e. as soon as a new device is detected "requester id" is allocated to it from available pool. When device is removed, return the "requester id" to pool. is there any h/w limitation which prevents it? Regards, Pankaj Bansal > > Thanks, > Jean > > > > > Is there a way to assign (and revoke) stream IDs at run time? > > > > Regards, > > Pankaj Bansal > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-ker...@lists.infradead.org > > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists > > .infradead.org%2Fmailman%2Flistinfo%2Flinux-arm- > kernel&data=02%7C0 > > > 1%7Cpankaj.bansal%40nxp.com%7C3cbe8bd4827e425afd0f08d6d54c925e%7C6 > 86ea > > > 1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636930922220665343&sda > ta=2La > > GBHO2%2Bbqk519uJvCatlHyRCtAPPjKO8Gxu1bQHBM%3D&reserved=0 > > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
