[PATCH v2 0/2] PCI: Fix the wrong reading of register fields

Jiwei Sun
2025-01-15T13:42:48Z

From: Jiwei Sun <sunjw10@lenovo.com>

Since commit de9a6c8d5dbf ("PCI/bwctrl: Add pcie_set_target_speed() to set
PCIe Link Speed"), there are two potential issues in the function
pcie_failed_link_retrain().

(1) The macro PCIE_LNKCTL2_TLS2SPEED() and PCIE_LNKCAP_SLS2SPEED() just
uses the link speed field of the registers. However, there are many other
different function fields in the Link Control 2 Register or the Link
Capabilities Register. If the register value is directly used by the two
macros, it may cause getting an error link speed value (PCI_SPEED_UNKNOWN).

(2) In the pcie_failed_link_retrain(), the local variable lnkctl2 is not
changed after reading from PCI_EXP_LNKCTL2. It might cause that the
removing 2.5GT/s downstream link speed restriction codes are not executed.

In order to avoid the above-mentioned potential issues, only keep link
speed field of the two registers before using and reread the Link Control 2
Register before using.

This series focuses on the first patch of the original series [1]. The
second one of the original series will submitted via the other single
patch.

Fixes: de9a6c8d5dbf ("PCI/bwctrl: Add pcie_set_target_speed() to set PCIe Link Speed")

[1] https://lore.kernel.org/linux-pci/tencent_DD9CBE5B44210B43A04EF8DAF52506A08509@qq.com/
---
v2 changes:
https://lore.kernel.org/linux-pci/tencent_753C9F9DFEC140A750F2778E6879E1049406@qq.com/
- divide the two issues into different patches
- get fixed inside the macros
---

Jiwei Sun (2):
PCI: Fix the wrong reading of register fields
PCI: reread the Link Control 2 Register before using

drivers/pci/pci.h | 30 +++++++++++++++++-------------
drivers/pci/quirks.c | 1 +
2 files changed, 18 insertions(+), 13 deletions(-)

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2.34.1