On Sun, Jan 18, 2026 at 09:26:45PM +0800, Hans Zhang wrote:

On 2025/12/31 10:58, Ricardo Pardini wrote:

quoted

On 27/11/2025 18:09, Hans Zhang wrote:

quoted

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)
   and not in PCIE_BUS_PEER2PEER mode (which requires default 128 bytes)
- 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 in v7:
- Exclude PCIE_BUS_PEER2PEER mode from Root Port MPS configuration
- Remove redundant check for upstream bridge (Root Ports don't have one)
- Improve commit message and code comments as per Bjorn.

Hi Hans,

I've tested on an Odroid-HC4 with a SATA SSD (via an ASM1061) by
applying your v7 on v6.19-rc3 + Bjorn's 20251103221930.1831376-1-
helgaas@kernel.org ("PCI: meson: Remove meson_pcie_link_up() timeout,
message, speed check" which is required to get the meson PCIe to work at
all since 6.18). With that setup I get:

# hdparm --direct -t /dev/sda
  Timing O_DIRECT disk reads: 832 MB in  3.00 seconds = 277.33 MB/sec

I've an identical machine, with a similar disk (even slightly faster, on
paper), running plain 6.12.y and there I get:

# hdparm --direct -t /dev/sda
  Timing O_DIRECT disk reads: 764 MB in  3.00 seconds = 254.26 MB/sec

I repeated those a few times, not very scientific, I know; but anyway:

Tested-by: Ricardo Pardini <redacted> # on Odroid-HC4

I've also feedback from another user running with this series with
success on a different meson PCIe machine, will ask them to TB as well;
they had reported a significant drop in performance since v6.18 without
this.

Hi,

Thank you very much for your test. Let's wait for Bjorn's reply.

Probably too late for the 6.20 / 7.0 merge window...

But.. it would be nice with some kind of feedback from Bjorn.

Is there any chance that this gets applied for 6.21/7.1 or is there
any fundamental objection against this series?


Kind regards,
Niklas