BUG: SiFive Unmatched: BAR0 on video card is never initialized

[Yuri Zaporozhets]

Hi Heinrich; hi all owners of SiFive Unmatched + PCIe video card,

Default U-Boot configuration for Unmatched always fails to initialize
BAR0 of my video card (NVidia GT710), because the PCI driver selects the MEMORY
region at 0x70000000 for bus_start/phys_start ("region 2", according to
decode_regions() output), which has the size of 0x1000000. Naturally, the
video card's BAR0 doesn't fit into this small region, because its size
is also 0x1000000:

  pci_auto_config_devices: start
  PCI Autoconfig: Bus Memory region: [70000000-70ffffff],
                  Physical Memory [70000000-70ffffff]
  PCI Autoconfig: Bus Prefetchable Mem region: [2000000000-3fffffffff],
                  Physical Memory [2000000000-3fffffffff]
  PCI Autoconfig: Bus I/O region: [60080000-6008ffff],
                  Physical Memory [60080000-6008ffff]
  .......
  pci_auto_config_devices: device pci_7:0.0
  PCI Autoconfig: BAR 0, Mem, size=0x1000000, bus_lower=0x70400000, bus_start=0x70000000, phys_start=0x70000000
  addr = 0x71000000
  No room in resource, avail start=70400000 / size=1000000, need=1000000
  PCI: Failed autoconfig bar 10

The situation changes drastically if CONFIG_PCI_REGION_MULTI_ENTRY is set to "yes".
After this, PCI starts to use "region 1" for MEMORY, which has the size of
0xFF70000, and is, obviously, suitable for GPU's BAR0:

pci_uclass_pre_probe, bus=-1/pcie at e00000000, parent=soc
decode_regions: len=28, cells_per_record=7
decode_regions: region 0, pci_addr=60080000, addr=60080000, size=10000, space_code=1
 - type=1, pos=0
decode_regions: region 1, pci_addr=60090000, addr=60090000, size=ff70000, space_code=2
 - type=0, pos=1
decode_regions: region 2, pci_addr=70000000, addr=70000000, size=1000000, space_code=2
 - type=0, pos=2
decode_regions: region 3, pci_addr=2000000000, addr=2000000000, size=2000000000, space_code=3
 - type=8, pos=3
....
PCIE-0: Link up (Gen1-x8, Bus0)
pci_uclass_post_probe: probing bus 0
pci_bind_bus_devices: bus 0/pcie at e00000000: found device 0, function 0: find ret=-19
pci_find_and_bind_driver: Searching for driver: vendor=f15e, device=0
pci_find_and_bind_driver: No match found: bound generic driver instead
pci_auto_config_devices: start
PCI Autoconfig: Bus Memory region: [60090000-6fffffff],
                Physical Memory [60090000-6fffffff]
PCI Autoconfig: Bus Prefetchable Mem region: [2000000000-3fffffffff],
                Physical Memory [2000000000-3fffffffff]
PCI Autoconfig: Bus I/O region: [60080000-6008ffff],
                Physical Memory [60080000-6008ffff]

This picture is in full accord with Linux kernel, which also uses
0x69000000 ("region 1") for bus_start and phys_start.

With this setting, all BARs on all devices are initialized correctly,
and, moreover, I can access memory-mapped VGA ports of the card (see [1] for
details), which is essential for initializing the card in text mode with
bios_emulator:

PCI Autoconfig: BAR 0, Mem, size=0x1000000, bus_lower=0x60500000, bus_start=0x60090000, phys_start=0x60090000
address=0x61000000 bus_lower=0x62000000

PCI Autoconfig: BAR 1, Prf64, size=0x8000000, bus_lower=0x2000000000, bus_start=0x2000000000, phys_start=0x2000000000
address=0x2000000000 bus_lower=0x2008000000

PCI Autoconfig: BAR 2, Prf64, size=0x2000000, bus_lower=0x2008000000, bus_start=0x2000000000, phys_start=0x2000000000
address=0x2008000000 bus_lower=0x200a000000

PCI Autoconfig: BAR 3, I/O, size=0x80, bus_lower=0x60080000, bus_start=0x60080000, phys_start=0x60080000
address=0x60080000 bus_lower=0x60080080

PCI Autoconfig: ROM, size=0x80000, bus_lower=0x62000000, bus_start=0x60090000, phys_start=0x60090000
address=0x62000000 bus_lower=0x62080000

Notes:

[1]: https://envytools.readthedocs.io/en/latest/hw/mmio.html#gf100-mmio-map

-- 
Regards,
Yuri