[PATCH v5 0/2] Configure root port MPS during host probing

[Hans Zhang]

Hi all，

I'm very sorry. I forgot the review label of Niklas. If it can be 
merged, please ask the maintainer to help add this tag. Thank you very much.

Reviewed-by: Niklas Cassel <cassel at kernel.org>

Best regards,
Hans

On 2025/6/20 23:55, Hans Zhang wrote:
> Current PCIe initialization exhibits a key optimization gap: Root Ports
> may operate with non-optimal Maximum Payload Size (MPS) settings. While
> downstream device configuration is handled during bus enumeration, Root
> Port MPS values inherited from firmware or hardware defaults often fail
> to utilize the full capabilities supported by controller hardware. This
> results in suboptimal data transfer efficiency throughout the PCIe
> hierarchy.
> 
> This patch series addresses this by:
> 
> 1.  Core PCI enhancement (Patch 1):
> - Proactively configures Root Port MPS during host controller probing
> - Sets initial MPS to hardware maximum (128 << dev->pcie_mpss)
> - Conditional on PCIe bus tuning being enabled (PCIE_BUS_TUNE_OFF unset)
> - Maintains backward compatibility via PCIE_BUS_TUNE_OFF check
> - Preserves standard MPS negotiation during downstream enumeration
> 
> 2.  Driver cleanup (Patch 2):
> - Removes redundant MPS configuration from Meson PCIe controller driver
> - Functionality is now centralized in PCI core
> - Simplifies driver maintenance long-term
> 
> ---
> Changes for v5:
> - Use pcie_set_mps directly instead of pcie_write_mps.
> - The patch 1 commit message were modified.
> 
> Changes for v4:
> - The patch [v4 1/2] add a comment to explain why it was done this way.
> - The patch [v4 2/2] have not been modified.
> - Drop patch [v3 3/3]. The Maintainer of the pci-aardvark.c file suggests
>    that this patch cannot be submitted. In addition, Mani also suggests
>    dropping this patch until this series of issues is resolved.
> 
> Changes for v3:
> - The new split is patch 2/3 and 3/3.
> - Modify the patch 1/3 according to Niklas' suggestion.
> 
> Changes for v2:
> - According to the Maintainer's suggestion, limit the setting of MPS
>    changes to platforms with controller drivers.
> - Delete the MPS code set by the SOC manufacturer.
> ---
> 
> Hans Zhang (2):
>    PCI: Configure root port MPS during host probing
>    PCI: dwc: Remove redundant MPS configuration
> 
>   drivers/pci/controller/dwc/pci-meson.c | 17 -----------------
>   drivers/pci/probe.c                    | 10 ++++++++++
>   2 files changed, 10 insertions(+), 17 deletions(-)
> 
> 
> base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494