+Tom Rini Hi Mark,
On Sat, 13 Mar 2021 at 02:24, Mark Kettenis <mark.kette...@xs4all.nl> wrote: > > I'm working on support for Apple's M1 systems in U-Boot. The idea is > that this can be used as a "payload" for the m1n1 bootloader that is > being developed by Hector Martin for Asahi Linux in order to provide > an UEFI implementation that can boot a standard arm64 OS. > > My current code, which can be found on the "apple-m1-m1n1" branch at: > > https://github.com/kettenis/u-boot/tree/apple-m1-m1n1 > > can already do this. I'm booting OpenBSD/arm64 this way and I've also > booted into grub using a standard arm64 Debian installer. > > One of the big challenges I'm facing is that the integrated PCIe > devices on the system sit behind an IOMMU that (as far as we can tell) > doesn't support any kind of bypass mode. I don't think we want full > IOMMU support in U-Boot, so the approach I'm currently taking is that > I set up the IOMMU to map a chunk of memory at the "top of RAM" where > U-Boot resides after relocation. But in order to use this mapping I > need to do DMA address translation. > > Fortunately Nicolas Saenz Julienne recently introduced > dev_phys_to_bus() and dev_bus_to_phys() interfaces to do this. Those > interfaces make use of a dma-ranges property in the device tree which > doesn't work so well for PCI devices though. However, the PCI code in > U-Boot already has a way to describe DMA address translation through > its regions support. Hooking this up to dev_phys_to_bus() and > dev_bus_to_phys() is fairly easy as illustrated by the diff below. > > Would this be viable approach? This could also help adding support > for PCIe devices on the Raspberry Pi CM4. It seems OK to me. I suspect IOMMU support will be needed to some degree eventually in U-Boot. Regards, Simon > > > commit 4f0e989c7a765291a38b7d10da562f23c5f31239 > Author: Mark Kettenis <kette...@openbsd.org> > Date: Fri Mar 12 20:23:11 2021 +0100 > > dm: Add PCI support to dev_phys_to_bus()/dev_bus_to_phys() > > For PCI devices, call dm_pci_phys_to_bus()/dm_pci_bus_to_phys() > to do the address translation. This uses the regions set up > by the PCI host controller driver to do the translation as a > single translation offset may not be sufficient in this case. > > Signed-off-by: Mark Kettenis <kette...@openbsd.org> > > diff --git a/include/phys2bus.h b/include/phys2bus.h > index 866b8b51a8..13d23ef4bb 100644 > --- a/include/phys2bus.h > +++ b/include/phys2bus.h > @@ -23,14 +23,21 @@ static inline unsigned long bus_to_phys(unsigned long bus) > > #if CONFIG_IS_ENABLED(DM) > #include <dm/device.h> > +#include <pci.h> > > static inline dma_addr_t dev_phys_to_bus(struct udevice *dev, phys_addr_t > phys) > { > + if (device_is_on_pci_bus(dev)) > + return dm_pci_phys_to_bus(dev, phys, PCI_REGION_SYS_MEMORY); > + > return phys - dev_get_dma_offset(dev); > } > > static inline phys_addr_t dev_bus_to_phys(struct udevice *dev, dma_addr_t > bus) > { > + if (device_is_on_pci_bus(dev)) > + return dm_pci_bus_to_phys(dev, bus, PCI_REGION_SYS_MEMORY); > + > return bus + dev_get_dma_offset(dev); > } > #else
