[v5,0/1] cxl/core/regs: Refactor out functions to count regblocks of given type

Message

Huaisheng Ye Jan. 15, 2025, 3:25 p.m. UTC

In commit d717d7f3df18494baafd9595fb4bcb9c380d7389, cxl_count_regblock was
added for counting regblocks of a given RBI (Register Block Identifier).
It is workable, but the implementation can be improved.

1. In order to get the count of instances, cxl_count_regblock has to tentatively
repeat the call of cxl_find_regblock_instance by increasing index from 0. It
will not stop until an error value is returned. Actually, It needs to search for
Register Blocks in dvsec again every time by taking a start from the head. The
operations can be optimized.

2. cxl_count_regblock blocks the opportunity to get error codes from
cxl_find_regblock_instance. cxl_pci_probe has error code checking for almost
all function calls. This is a good behavior, but existing cxl_count_regblock
couldn't return error codes.

With this patch, only need to have minor modifications in
__cxl_find_regblock_instance, which can return the count of regblocks by given
RBI in just one call. It is more effective than before. Besides, the error code
could be obtained by the called function, here is cxl_pci_probe.

---

This patch is tested by ndctl cxl_test and physical CXL expander card
with v6.13-rc6.

1. Ndctl CXL test suite v80 could pass with this patch applied.
$ meson test -C build --suite cxl
ninja: Entering directory `/home/work/source/ndctl/build'
[1/48] Generating version.h with a custom command
 1/11 ndctl:cxl / cxl-topology.sh               OK               3.48s
 2/11 ndctl:cxl / cxl-region-sysfs.sh           OK               2.74s
 3/11 ndctl:cxl / cxl-labels.sh                 OK               1.75s
 4/11 ndctl:cxl / cxl-create-region.sh          OK               3.51s
 5/11 ndctl:cxl / cxl-xor-region.sh             OK               1.89s
 6/11 ndctl:cxl / cxl-events.sh                 OK               1.63s
 7/11 ndctl:cxl / cxl-sanitize.sh               OK               4.48s
 8/11 ndctl:cxl / cxl-destroy-region.sh         OK               1.90s
 9/11 ndctl:cxl / cxl-qos-class.sh              OK               2.65s
10/11 ndctl:cxl / cxl-poison.sh                 OK               2.86s
11/11 ndctl:cxl / cxl-security.sh               OK               0.91s

2. Test patch with Qemu x4 switch topology:

                       ACPI0017:00 [root0]
                           |
                         HB_0 [port1]
                        /             \
                     RP_0             RP_1
                      |                 |
                USP [port2]
            /    /    \    \
          DSP   DSP   DSP   DSP
           |     |     |     |
          mem1  mem0  mem2  mem3

Every card has 2 PMU RBs, here are the pmu_mem devices.

$ pwd
/sys/bus/cxl/devices
$ tree
[snip]
├── pmu_mem0.0 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:01.0/0000:10:00.0/pmu_mem0.0
├── pmu_mem0.1 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:01.0/0000:10:00.0/pmu_mem0.1
├── pmu_mem1.0 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:00.0/0000:0f:00.0/pmu_mem1.0
├── pmu_mem1.1 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:00.0/0000:0f:00.0/pmu_mem1.1
├── pmu_mem2.0 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:02.0/0000:11:00.0/pmu_mem2.0
├── pmu_mem2.1 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:02.0/0000:11:00.0/pmu_mem2.1
├── pmu_mem3.0 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:03.0/0000:12:00.0/pmu_mem3.0
├── pmu_mem3.1 -> ../../../devices/pci0000:0c/0000:0c:00.0/0000:0d:00.0/0000:0e:03.0/0000:12:00.0/pmu_mem3.1

---

Changes
=======
v4 -> v5:
1. Fix lkp auto build test WARNING about kernel-doc
 [v4] https://lore.kernel.org/all/[e-mail]/

=======
v3 -> v4:
1. Simplify code comments of __cxl_find_regblock_instance() (Jonathan)
2. Move testing setup to cover letter (Jonathan)
3. Get Reviewed-by from Jonathan

=======
v2 -> v3:
1. Create static function __cxl_find_regblock_instance() for implementation of
   locating a register block or counting instances by type / index
   underneath. (Jonathan)
2. cxl_count_regblock() and cxl_find_regblock_instance() respectively call
   __cxl_find_regblock_instance for the purpose of counting instances and
   locating RB. (Jonathan)
3. Change parameter index's type to 'unsigned int' in cxl_find_regblock_instance (Jonathan)
4. Rebase patch to v6.13-rc6

=======
v1 -> v2:
1. Reserved cxl_count_regblock() for original function interface (Ming)
2. Reset 'map->resource' to 'CXL_RESOURCE_NONE' before returning the count of instances in
   cxl_find_regblock_instance() (Ming)
3. Append results of ndctl test suite and Qemu testing PMU devices to commit log (Ming)
4. Rebase patch to v6.13-rc5

Huaisheng Ye (1):
  cxl/core/regs: Refactor out functions to count regblocks of given type

 drivers/cxl/core/regs.c | 54 +++++++++++++++++++++++++----------------
 drivers/cxl/cxl.h       |  3 ++-
 drivers/cxl/pci.c       |  6 ++++-
 3 files changed, 40 insertions(+), 23 deletions(-)