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

[Conor Dooley <conor@kernel.org>]

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Hey folks,

Has this patchset fallen through the cracks?

Cheers,
Conor.

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.


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