Re: [PATCH v10 0/3] Fix address translations on MPFS PCIe controller

Bjorn Helgaas
2025-01-14T23:19:40Z

On Tue, Jan 14, 2025 at 05:16:10PM +0000, Conor Dooley wrote:
> Hey folks,
>
> Has this patchset fallen through the cracks?

Yes, unfortunately. I applied it to pci/controller/microchip for
v6.14.

I had to adapt it slightly to account for the changes of ac7f53b7e728
("PCI: microchip: Add support for using either Root Port 1 or 2"), so
please take a look and make sure I did it right.

> On Wed, Nov 13, 2024 at 11:50:44AM +0000, Conor Dooley wrote:
> > On Fri, Oct 11, 2024 at 03:00:40PM +0100, daire.mcnamara@microchip.com wrote:
> > > From: Daire McNamara <daire.mcnamara@microchip.com>
> > >
> > > Hi all,
> > >
> > > On Microchip PolarFire SoC (MPFS), the PCIe controller is connected to the
> > > CPU via one of three Fabric Interface Connectors (FICs). Each FIC present
> > > to the CPU complex as 64-bit AXI-M and 64-bit AXI-S. To preserve
> > > compatibility with other PolarFire family members, the PCIe controller is
> > > connected to its encapsulating FIC via a 32-bit AXI-M and 32-bit AXI-S
> > > interface.
> > >
> > > Each FIC is implemented in FPGA logic and can incorporate logic along its 64-bit
> > > AXI-M to 32-bit AXI-M chain (including address translation) and, likewise, along
> > > its 32-bit AXI-S to 64-bit AXI-S chain (again including address translation).
> > >
> > > In order to reduce the potential support space for the PCIe controller in
> > > this environment, MPFS supports certain reference designs for these address
> > > translations: reference designs for cache-coherent memory accesses
> > > and reference designs for non-cache-coherent memory accesses. The precise
> > > details of these reference designs and associated customer guidelines
> > > recommending that customers adhere to the addressing schemes used in those
> > > reference designs are available from Microchip, but the implication for the
> > > PCIe controller address translation between CPU-space and PCIe-space are:
> > >
> > > For outbound address translation, the PCIe controller address translation tables
> > > are treated as if they are 32-bit only. Any further address translation must
> > > be done in FPGA fabric.
> > >
> > > For inbound address translation, the PCIe controller is configurable for two
> > > cases:
> > > * In the case of cache-coherent designs, the base of the AXI-S side of the
> > > address translation must be set to 0 and the size should be 4 GiB wide. The
> > > FPGA fabric must complete any address translations based on that 0-based
> > > address translation.
> > > * In the case of non-cache coherent designs, the base of AXI-S side of the
> > > address translation must be set to 0x8000'0000 and the size shall be 2 GiB
> > > wide. The FPGA fabric must complete any address translation based on that
> > > 0x80000000 base.
> > >
> > > So, for example, in the non-cache-coherent case, with a device tree property
> > > that maps an inbound range from 0x10'0000'0000 in PCIe space to 0x10'0000'0000
> > > in CPU space, the PCIe rootport will translate a PCIe address of 0x10'0000'0000
> > > to an intermediate 32-bit AXI-S address of 0x8000'0000 and the FIC is
> > > responsible for translating that intermediate 32-bit AXI-S address of
> > > 0x8000'0000 to a 64-bit AXI-S address of 0x10'0000'0000.
> > >
> > > And similarly, for example, in the cache-coherent case, with a device tree
> > > property that maps an inbound range from 0x10'0000'0000 in PCIe space to
> > > 0x10'0000'0000 in CPU space, the PCIe rootport will translate a PCIe address
> > > of 0x10'0000'0000 to an intermediate 32-bit AXI-S address of 0x0000'0000 and
> > > the FIC is responsible for translating that intermediate 32-bit AXI-S address
> > > of 0x0000'0000 to a 64-bit AXI-S address of 0x10'0000'0000.
> > >
> > > See https://lore.kernel.org/all/20220902142202.2437658-1-daire.mcnamara@microchip.com/T/
> > > for backstory.
> > >
> > > Changes since v9:
> > > - Dropped plda_setup_inbound_address_translation() from StarFive driver
> >
> > Since I had some success bumping the other series for this driver, any
> > chance of some attention here?
> > AFAIK, Daire's addressed what's been pointed out by reviewers and
> > exempted the StarFive driver from overwriting the firmware-set values
> > with once calculated from DT as they requested.
>