[PATCH v6 0/3] PCI: rockchip: 5.0 GT/s speed discouraged by Rockchip

[Geraldo Nascimento]

Dragan Simic already had warned me of potential issues with 5.0 GT/s
speed operation in Rockchip PCIe. However, in recent interactions
with Shawn Lin from Rockchip it came to my attention there's grave
danger in the unknown errata regarding 5.0 GT/s operational speed
of their PCIe core, including data loss.

Drop all code related to 5.0 GT/s operational speed from this driver.

Endpoint Mode driver was not tested.

---
Changes in v6:
- Squashed patches 3 & 4 together as suggested by Mani
- More formal warning message as suggested by Dragan
- Set the 2.5 GT/s bit regardless of if link-speed is set to 2
- Link to v5: https://lore.kernel.org/all/cover.1772239598.git.geraldogabriel@xxxxxxxxx/T/

Changes in v5:
- Changed commit order to not break builds and adjusted copy pasted
  commit message. (thanks Charalampos!)
- Reintroduced behavior to force 2.5 GT/s in case there's something
  non-default in the DT. (thanks Dragan!)
- Link to v4: https://lore.kernel.org/linux-rockchip/cover.1772169998.git.geraldogabriel@xxxxxxxxx/T/

Changes in v4:
- Incorporate suggestion by Bjorn and refined by Dragan to drop the
  "catastrophic" code
- Link to v3: https://lore.kernel.org/linux-rockchip/cover.1772057799.git.geraldogabriel@xxxxxxxxx/T/

Changes in v3:
- Clarify warning message even though Rockchip won't disclose details
- Drop DT changes as they were applied as subset by Heiko
- Link to v2: https://lore.kernel.org/all/cover.1763415705.git.geraldogabriel@xxxxxxxxx/T/

Changes in v2:
- hard limit to 2.5 GT/s, not just warn
- add Reported-by: and Reviewed-by: Dragan Simic
- remove redundant declaration of max-link-speed from helios64 dts
- fix Link: of helios64 patch
- simplify RC mode comment
- Link to v1: https://lore.kernel.org/all/aRhR79u5BPtRRFw3@geday/T/

---

Geraldo Nascimento (3):
  PCI: rockchip-ep: do not attempt 5.0 GT/s retraining
  PCI: rockchip-host: do not attempt 5.0 GT/s retraining
  PCI: rockchip: drive at 2.5 GT/s, error other speeds

 drivers/pci/controller/pcie-rockchip-ep.c   | 13 -------------
 drivers/pci/controller/pcie-rockchip-host.c | 20 --------------------
 drivers/pci/controller/pcie-rockchip.c      | 16 +++++++++-------
 drivers/pci/controller/pcie-rockchip.h      |  3 ---
 4 files changed, 9 insertions(+), 43 deletions(-)

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2.54.0