[RFC PATCH 0/3] PCI: Add PCIe Gen 7 (128 GT/s) speed support

["Ionut Nechita (Sunlight Linux)" <sunlightlinux@gmail.com>]

From: Ionut Nechita <ionut_n2001@yahoo.com>

This RFC series adds initial kernel support for PCIe Gen 7 128 GT/s
link speed, following the same pattern used for Gen 6 (64 GT/s).

PCIe Gen 7 doubles the per-lane data rate to 128 GT/s using PAM4
signaling with mandatory Flit mode encoding (1:1, no overhead),
providing up to 256 GB/s unidirectional (512 GB/s bi-directional)
bandwidth on an x16 link. The specification was announced by PCI-SIG
in 2022 and targeted for member release in 2025.

The series covers:

  Patch 1: UAPI register definitions (LNKCAP, LNKCAP2, LNKCTL2) and
           pci_bus_speed enum. Widens supported_speeds from u8 to u16
           to accommodate the expanded Supported Link Speeds Vector.

  Patch 2: Core PCI infrastructure - speed detection macros, bandwidth
           calculation with 1:1 Flit mode encoding, link speed table,
           display string, and a pcie_speed_requires_flit() helper
           with Flit mode diagnostic warning for Gen 6+ speeds.

  Patch 3: Subsystem updates for bandwidth control (bwctrl), port
           driver, and PCIe thermal cooling.

Not included in this series (not yet defined in the specification):
  - Equalization presets for 128 GT/s (PCI_EXT_CAP_ID_PL_128GT)
  - DesignWare controller preset programming for Gen 7

This is marked as RFC since no PCIe Gen 7 hardware exists yet to
validate the implementation. The register encoding values (LNKCAP
SLS=0x7, LNKCAP2 SLS bit 6, LNKCTL2 TLS=0x7) follow the sequential
pattern established by prior generations and are subject to change
when the final specification is published.

Tested: compile-tested only (no hardware available).

Ionut Nechita (3):
  PCI: Add PCIe Gen 7 (128 GT/s) register and speed definitions
  PCI: Add PCIe Gen 7 (128 GT/s) speed detection and reporting
  PCI: Update bandwidth control and thermal cooling for Gen 7 (128 GT/s)

 drivers/pci/pci.c              |  7 +++++--
 drivers/pci/pci.h              | 28 ++++++++++++++++++++++------
 drivers/pci/pcie/bwctrl.c      |  7 ++++---
 drivers/pci/pcie/portdrv.c     |  2 +-
 drivers/pci/probe.c            |  3 ++-
 drivers/thermal/pcie_cooling.c |  1 +
 include/linux/pci.h            |  3 ++-
 include/uapi/linux/pci_regs.h  |  3 +++
 8 files changed, 40 insertions(+), 14 deletions(-)

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2.53.0