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Date: Tue, 11 Feb 2020 15:55:20 +0200 From: Laurentiu Tudor <laurentiu.tudor@....com> To: Robin Murphy <robin.murphy@....com>, Li Yang <leoyang.li@....com>, Olof Johansson <olof@...om.net> Cc: "mark.rutland@....com" <mark.rutland@....com>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, "arnd@...db.de" <arnd@...db.de>, "m.karthikeyan@...iveil.co.in" <m.karthikeyan@...iveil.co.in>, "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, "Z.q. Hou" <zhiqiang.hou@....com>, "l.subrahmanya@...iveil.co.in" <l.subrahmanya@...iveil.co.in>, "will.deacon@....com" <will.deacon@....com>, Russell King - ARM Linux admin <linux@...linux.org.uk>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "M.h. Lian" <minghuan.lian@....com>, "robh+dt@...nel.org" <robh+dt@...nel.org>, Xiaowei Bao <xiaowei.bao@....com>, "catalin.marinas@....com" <catalin.marinas@....com>, "bhelgaas@...gle.com" <bhelgaas@...gle.com>, "andrew.murray@....com" <andrew.murray@....com>, "shawnguo@...nel.org" <shawnguo@...nel.org>, Mingkai Hu <mingkai.hu@....com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Diana Madalina Craciun <diana.craciun@....com> Subject: Re: [PATCHv9 00/12] PCI: Recode Mobiveil driver and add PCIe Gen4 driver for NXP Layerscape SoCs On 11.02.2020 15:04, Robin Murphy wrote: > On 2020-02-11 12:13 pm, Laurentiu Tudor wrote: > [...] >>> This is a known issue about DPAA2 MC bus not working well with SMMU >>> based IO mapping. Adding Laurentiu to the chain who has been looking >>> into this issue. >> >> Yes, I'm closely following the issue. I actually have a workaround >> (attached) but haven't submitted as it will probably raise a lot of >> eyebrows. In the mean time I'm following some discussions [1][2][3] on >> the iommu list which seem to try to tackle what appears to be a >> similar issue but with framebuffers. My hope is that we will be able >> to leverage whatever turns out. > > Indeed it's more general than framebuffers - in fact there was a > specific requirement from the IORT side to accommodate network/storage > controllers with in-memory firmware/configuration data/whatever set up > by the bootloader that want to be handed off 'live' to Linux because the > overhead of stopping and restarting them is impractical. Thus this DPAA2 > setup is very much within scope of the desired solution, so please feel > free to join in (particularly on the DT parts) :) Will sure do. Seems that the 2nd approach (the one with list of compatibles in arm-smmu) fits really well with our scenario. Will this be the way to go forward? > As for right now, note that your patch would only be a partial > mitigation to slightly reduce the fault window but not remove it > entirely. To be robust the SMMU driver *has* to know about live streams > before the first arm_smmu_reset() - hence the need for generic firmware > bindings - so doing anything from the MC driver is already too late (and > indeed the current iommu_request_dm_for_dev() mechanism is itself a > microcosm of the same problem). I think you might have missed in the patch that it pauses the firmware at early boot, in its driver init and it resumes it only after iommu_request_dm_for_dev() has completed. :) --- Best Regards, Laurentiu
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