[PATCH v4 0/2] Add support for RAS DES feature in PCIe DW

[Shradha Todi]

DesignWare controller provides a vendor specific extended capability
called RASDES as an IP feature. This extended capability  provides
hardware information like:
 - Debug registers to know the state of the link or controller. 
 - Error injection mechanisms to inject various PCIe errors including
   sequence number, CRC
 - Statistical counters to know how many times a particular event
   occurred

However, in Linux we do not have any generic or custom support to be
able to use this feature in an efficient manner. This is the reason we
are proposing this framework. Debug and bring up time of high-speed IPs
are highly dependent on costlier hardware analyzers and this solution
will in some ways help to reduce the HW analyzer usage.

The debugfs entries can be used to get information about underlying
hardware and can be shared with user space. Separate debugfs entries has
been created to cater to all the DES hooks provided by the controller.
The debugfs entries interacts with the RASDES registers in the required
sequence and provides the meaningful data to the user. This eases the
effort to understand and use the register information for debugging.

v4:
    - Addressed comments from Manivannan, Bjorn and Jonathan
    - Addressed style related change requests from v3
    - Added Documentation under Documentation/ABI/testing and kdoc stype
      comments wherever required for better understanding
    - Enhanced error injection to include all possible error groups
    - Removed debugfs init call from common designware file and left it
      up to individual platform drivers to init/deinit as required.

v3: https://lore.kernel.org/all/20240625093813.112555-1-shradha.t@xxxxxxxxxxx/
    - v2 had suggestions about moving this framework to perf/EDAC instead of a
      controller specific debugfs but after discussions we decided to go ahead
      with the same. Rebased and posted v3 with minor style changes.

v2: https://lore.kernel.org/lkml/20231130115044.53512-1-shradha.t@xxxxxxxxxxx/
    - Addressed comments from Krzysztof Wilczyński, Bjorn Helgaas and
      posted v2 with a changed implementation for a better code design

v1: https://lore.kernel.org/all/20210518174618.42089-1-shradha.t@xxxxxxxxxxx/T/

Shradha Todi (2):
  PCI: dwc: Add support for vendor specific capability search
  PCI: dwc: Add debugfs based RASDES support in DWC

 Documentation/ABI/testing/debugfs-dwc-pcie    | 143 +++++
 drivers/pci/controller/dwc/Kconfig            |  11 +
 drivers/pci/controller/dwc/Makefile           |   1 +
 .../controller/dwc/pcie-designware-debugfs.c  | 544 ++++++++++++++++++
 .../controller/dwc/pcie-designware-debugfs.h  |   0
 drivers/pci/controller/dwc/pcie-designware.c  |  16 +
 drivers/pci/controller/dwc/pcie-designware.h  |  18 +
 7 files changed, 733 insertions(+)
 create mode 100644 Documentation/ABI/testing/debugfs-dwc-pcie
 create mode 100644 drivers/pci/controller/dwc/pcie-designware-debugfs.c
 create mode 100644 drivers/pci/controller/dwc/pcie-designware-debugfs.h

-- 
2.17.1