On Wed, Jul 03, 2024 at 01:09:43PM -0700, Palmer Dabbelt wrote: > On Mon, 10 Jun 2024 04:09:12 PDT (-0700), Conor Dooley wrote: > > Hey all, > > > > Here's some patches that add an Erratum to enable non-coherent DMA > > support for PolarFire SoC. By nature of being an FPGA, and due to the > > PCIe root ports being only 32-bit capable, many bitstreams configure the > > FPGA fabric such that peripherals in the fabric become non-coherent. The > > PCIe root ports on PolarFire SoC are connected to the core-complex via > > the fabric, and therefore can be (and regularly are) made DMA > > non-coherent. The Icicle Kit Reference Design has been configuring the > > PCIe root port in this manner since late 2022 and in a way unsupported > > by mainline since earlier that year. Adding this non-coherent DMA > > support makes PCIe functional on those FPGA designs. Daire did almost all > > the work to figure out how to support these kinds of designs, and this > > series depends on his patches to introduce the required dma-ranges > > handling for the root port driver: > > https://lore.kernel.org/linux-pci/20240531085333.2501399-1-daire.mcnamara@xxxxxxxxxxxxx/ > > > > The final patch depends on: > > https://lore.kernel.org/linux-pci/20240527-slather-backfire-db4605ae7cd7@wendy/ > > > > I'm not sure if an Erratum is really the right way to go about doing > > this, but I didn't want to make ARCH_MICROCHIP depend on NONPORTABLE. > > An alternative would be to add a menu under drivers/soc like Renesas > > does and allow it to be toggled as an option there instead. > > Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx> > > if you want to take this via some other tree. Yeah, I was expecting to take it myself but hadn't gone fishing for an ack because the PCI parts haven't landed yet & the copy in my k.org tree had a KISMET issue reported against it. > I don't see any issue calling it an erratum, if it lets us keep building > generic kernels for these systems that seems like a good enough agrument to > me. Cool :)
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