[PATCH v3 0/3] Display cxl1.1 device link status

From: "Kobayashi,Daisuke" <kobayashi.da-06@fujitsu.com>
To: kobayashi.da-06@jp.fujitsu.com, linux-cxl@vger.kernel.org
Cc: y-goto@fujitsu.com, linux-pci@vger.kernel.org, mj@ucw.cz,
	dan.j.williams@intel.com,
	"Kobayashi,Daisuke" <kobayashi.da-06@fujitsu.com>
Subject: [PATCH v3 0/3] Display cxl1.1 device link status
Date: Tue, 12 Mar 2024 17:05:56 +0900	[thread overview]
Message-ID: <20240312080559.14904-1-kobayashi.da-06@fujitsu.com> (raw)

Hello.

This patch series adds a feature that displays the link status
of the CXL1.1 device.

CXL devices are extensions of PCIe. Therefore, from CXL2.0 onwards,
the link status can be output in the same way as traditional PCIe.
However, unlike devices from CXL2.0 onwards, CXL1.1 requires a
different method to obtain the link status from traditional PCIe.
This is because the link status of the CXL1.1 device is not mapped
in the configuration space (as per cxl3.0 specification 8.1).
Instead, the configuration space containing the link status is mapped
to the memory mapped register region (as per cxl3.0 specification 8.2,
Table 8-18). Therefore, the current lspci has a problem where it does
not display the link status of the CXL1.1 device. 
This patch solves these issues.

The procedure is as follows:
First, obtain the RCRB address within the cxl driver, then access 
the configuration space. Next, output the link status information from
the configuration space to sysfs. Finally, read sysfs within lspci to 
display the link status information.

Changes
v1[1] -> v2:
The following are the main changes made based on the feedback from Dan Williams.
- Modified to perform rcrb access within the CXL driver.
- Added new attributes to the sysfs of the PCI device.
- Output the link status information to the sysfs of the PCI device.
- Retrieve information from sysfs as the source when displaying information in lspci.

v2[2] -> v3:
- Fix unnecessary initialization and wrong types (Bjohn).
- Create a helper function for getting a PCIe capability offset (Bjohn).
- Move platform-specific implementation to the lib directory in pciutils (Martin).

[1]
https://lore.kernel.org/linux-cxl/20231220050738.178481-1-kobayashi.da-06@fujitsu.com/
[2]
https://lore.kernel.org/linux-cxl/20240227083313.87699-1-kobayashi.da-06@fujitsu.com/

Kobayashi,Daisuke (3):
  Add sysfs attribute for CXL 1.1 device link status
  Remove conditional branch that is not suitable for cxl1.1 devices

 drivers/cxl/acpi.c |   4 -
 drivers/cxl/pci.c  | 193 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 193 insertions(+), 4 deletions(-)

  Add function to display cxl1.1 device link status

 lib/access.c | 29 +++++++++++++++++++++
 lib/pci.h    |  2 ++
 ls-caps.c    | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+)
-- 
2.43.0