[PATCH v3 0/6] MIPS: ralink: fix PCI IO resources

From: Sergio Paracuellos
Date: Sat Sep 25 2021 - 16:32:39 EST

MIPs ralink need a special tratement regarding the way it handles PCI IO
resources. On MIPS I/O ports are memory mapped, so we access them using normal
load/store instructions. MIPS 'plat_mem_setup()' function does a call to
'set_io_port_base(KSEG1)'. There, variable 'mips_io_port_base'
is set then using this address which is a virtual address to which all
ports are being mapped. Ralink I/O space has a mapping of bus address
equal to the window into the mmio space, with an offset of IO start range
cpu address. This means that to have this working we need:
- linux port numbers in the range 0-0xffff.
- pci port numbers in the range 0-0xffff.
- io_offset being zero.

These means at the end to have bus address 0 mapped to IO range cpu address.
We need a way of properly set 'mips_io_port_base' with a virtually mapped
value of the IO cpu address.

This series do the following approach:
1) Revert two bad commit from a previous attempt of make this work [0].
2) Set PCI_IOBASE to mips 'mips_io_port_base'.
3) Allow architecture dependent 'pci_remap_iospace'.
4) Implement 'pci_remap_iospace' for MIPS.
5) Be sure IOBASE address for IO window is set with correct value.

More context about this series appoach in this mail thread [1].

Patches related with reverts are from this merge cycle so they are only
added to the staging git tree. So to have all stuff together I'd like to
get everybody Ack's to get all of this series through staging tree if
possible :).

Thanks in advance for your time.

Changes in v3:
- Collect Arnd's Acked-by for the patches.
- Be sure IO resource start address is zero and WARN_ONCE if it is not
on MIPS pci_remap_iospace() patch. Also make use of 'resource_size'
instead of do the logic explicitly again.

Changes in v2:
- re-do commit messages for PCI patch as Bjorn pointed out in previous series.
- Add Bjorn's Acked-by for PCI subsystem patch.
- Re-do commit message of MIPS 'pci_remap_iospace()' patch to align with changes
in the PCI patch (s/architecture dependent/architecture-specific/)
- Add Fixes-by tag for MIPS set PCI_IOBASE patch.

[0]: https://www.spinics.net/lists/kernel/msg4051474.html
[1]: https://lkml.org/lkml/2021/9/22/6
Sergio Paracuellos (6):
Revert "MIPS: ralink: don't define PC_IOBASE but increase
Revert "staging: mt7621-pci: set end limit for 'ioport_resource'"
MIPS: ralink: set PCI_IOBASE to 'mips_io_port_base'
PCI: Allow architecture-specific pci_remap_iospace()
MIPS: implement architecture-specific 'pci_remap_iospace()'
staging: mt7621-pci: properly adjust base address for the IO window

arch/mips/include/asm/mach-ralink/spaces.h | 4 +++-
arch/mips/include/asm/pci.h | 2 ++
arch/mips/pci/pci-generic.c | 14 ++++++++++++++
drivers/pci/pci.c | 2 ++
drivers/staging/mt7621-pci/pci-mt7621.c | 4 +---
5 files changed, 22 insertions(+), 4 deletions(-)