Hi Mark!
On Sat, 2021-03-13 at 10:24 +0100, Mark Kettenis wrote: [...]
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.
Why doesn't it work with PCI devices? Raspberry Pi 4 has a PCIe bus that needs DMA translations. This is handled by parsing its 'dma-ranges' property. Here's how rpi4's devicetree looks like[1]:
pcie0: pcie@7d500000 { compatible = "brcm,bcm2711-pcie"; ranges = <0x02000000 0x0 0xf8000000 0x6 0x00000000 0x0 0x04000000>; /* * The wrapper around the PCIe block has a bug preventing it * from accessing beyond the first 3GB of memory. */ dma-ranges = <0x02000000 0x0 0x00000000 0x0 0x00000000 0x0 0xc0000000>; };
However, the PCI code in U-Boot already has a way to describe DMA address translation through its regions support.
regions contain a representation of devicetree's 'ranges' property, which doesn't describe the DMA address translations, but CPU's view of PCI memory.
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);
Note that this would break USB support on RPi4.
Regards, Nicolas
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch...