Re: [PATCH v4 0/7] Improve PCI memory mapping API

[Damien Le Moal <dlemoal@kernel.org>]

On 10/7/24 13:03, Damien Le Moal wrote:
> This series introduces the new functions pci_epc_map_align(),
> pci_epc_mem_map() and pci_epc_mem_unmap() to improve handling of the
> PCI address mapping alignment constraints of endpoint controllers in a
> controller independent manner.
> 
> The issue fixed is that the fixed alignment defined by the "align" field
> of struct pci_epc_features is defined for inbound ATU entries (e.g.
> BARs) and is a fixed value, whereas some controllers need a PCI address
> alignment that depends on the PCI address itself. For instance, the
> rk3399 SoC controller in endpoint mode uses the lower bits of the local
> endpoint memory address as the lower bits for the PCI addresses for data
> transfers. That is, when mapping local memory, one must take into
> account the number of bits of the RC PCI address that change from the
> start address of the mapping.
> 
> To fix this, the new endpoint controller method .map_align is introduced
> and called from pci_epc_map_align(). This method is optional and for
> controllers that do not define it, it is assumed that the controller has
> no PCI address constraint.
> 
> The functions pci_epc_mem_map() is a helper function which obtains
> mapping information, allocates endpoint controller memory according to
> the mapping size obtained and maps the memory. pci_epc_mem_unmap()
> unmaps and frees the endpoint memory.
> 
> This series is organized as follows:
>  - Patch 1 introduces a small helper to clean up the epc core code
>  - Patch 2 improves pci_epc_mem_alloc_addr()
>  - Patch 3 and 4 introduce the new map_align endpoint controller method
>    and the epc functions pci_epc_mem_map() and pci_epc_mem_unmap().
>  - Patch 5 documents these new functions.
>  - Patch 6 modifies the test endpoint function driver to use 
>    pci_epc_mem_map() and pci_epc_mem_unmap() to illustrate the use of
>    these functions.
>  - Finally, patch 7 implements the rk3588 endpoint controller driver
>    .map_align operation to satisfy that controller PCI address
>    alignment constraint.

I forgot to add that the series was extensively tested using the rk3588 endpoint
controller with the test endpoint function driver (as-is and modified to remove
the forced host buffer alignment) as well as using the NVMe endpoint function
driver (v1 patches just posted).

> 
> Changes from v3:
>  - Addressed Niklas comments (improved patch 2 commit message, added
>    comments in the pci_epc_map_align() function in patch 3, typos and
>    improvements in patch 5, patch 7 commit message).
>  - Added review tags
> 
> Changes from v2:
>  - Dropped all patches for the rockchip-ep. These patches will be sent
>    later as a separate series.
>  - Added patch 2 and 5
>  - Added review tags to patch 1
> 
> Changes from v1:
>  - Changed pci_epc_check_func() to pci_epc_function_is_valid() in patch
>    1.
>  - Removed patch "PCI: endpoint: Improve pci_epc_mem_alloc_addr()"
>    (former patch 2 of v1)
>  - Various typos cleanups all over. Also fixed some blank space
>    indentation.
>  - Added review tags
> 
> Damien Le Moal (7):
>   PCI: endpoint: Introduce pci_epc_function_is_valid()
>   PCI: endpoint: Improve pci_epc_mem_alloc_addr()
>   PCI: endpoint: Introduce pci_epc_map_align()
>   PCI: endpoint: Introduce pci_epc_mem_map()/unmap()
>   PCI: endpoint: Update documentation
>   PCI: endpoint: test: Use pci_epc_mem_map/unmap()
>   PCI: dwc: endpoint: Define the .map_align() controller operation
> 
>  Documentation/PCI/endpoint/pci-endpoint.rst   |  35 ++
>  .../pci/controller/dwc/pcie-designware-ep.c   |  15 +
>  drivers/pci/endpoint/functions/pci-epf-test.c | 372 +++++++++---------
>  drivers/pci/endpoint/pci-epc-core.c           | 223 ++++++++---
>  drivers/pci/endpoint/pci-epc-mem.c            |   9 +-
>  include/linux/pci-epc.h                       |  41 ++
>  6 files changed, 465 insertions(+), 230 deletions(-)
> 


-- 
Damien Le Moal
Western Digital Research