[PATCH v6 0/6] clk: Support spread spectrum and use it in clk-scmi

[Peng Fan (OSS)]

Since the assigned-clock-sscs property [1] has been accepted into the device
tree schema, we can now support it in the Linux clock driver. Therefore,
I've picked up the previously submitted work [2] titled "clk: Support
spread spectrum and use it in clk-pll144x and clk-scmi."
As more than six months have passed since [2] was posted, I’m treating this
patchset as a new submission rather than a v3.

- Introduce clk_set_spread_spectrum to set the parameters for enabling
  spread spectrum of a clock.
- Parse 'assigned-clock-sscs' and configure it by default before using the
  clock. This property is parsed before parsing clock rate.
- Enable this feature for clk-scmi on i.MX95.

Because SCMI spec will not include spread spectrum as a standard
extension, we still need to use NXP i.MX OEM extension.

[1] https://github.com/devicetree-org/dt-schema/pull/154
[2] https://lore.kernel.org/all/20250205-clk-ssc-v2-0-fa73083caa92@nxp.com/

Signed-off-by: Peng Fan <peng.fan at nxp.com>
---
Changes in v6:
- Add kunit build warning
- Update OEM string comparation per Sebin

Changes in v5:
- Per Stephen, export clk_hw_set_spread_spectrum, use enum for method,
  add const for set_spread_spectrum and rename clk_ss/conf to ss_conf.
- Per Sebin, Cristian, Sudeep, I added clk-scmi-oem.c to support vendor
  extensions.
- Link to v4: https://lore.kernel.org/arm-scmi/aNQPWO6pfA_3mmxf@redhat.com/T/#me81231bf286e2a8e4e00a68707ed1e525a2b4a3d

Changes in v4:
- Add R-b for patch 1 from Brian
- Drop unecessary change in patch 4 Per Brian
- Link to v3: https://lore.kernel.org/r/20250912-clk-ssc-version1-v3-0-fd1e07476ba1@nxp.com

Changes in v3:
- New patch 1 for dt-bindings per comment from Brian
  https://lore.kernel.org/all/aLeEFzXkPog_dt2B@x1/
  This might not be good to add a new dt-binding file in v3. But this is
  quite a simple file that just has four macros to encode modulation
  method. So hope this is fine for DT maintainers.
- Add Brain's R-b for patch 2
- New patch 3 to add Kunit test per Brain. Since Brain helped
  draft part of the code, I added Co-developed-by tag from Brain.
- Link to v2: https://lore.kernel.org/r/20250901-clk-ssc-version1-v2-0-1d0a486dffe6@nxp.com

Changes in v2:
- Simplify the code in patch 2 per Dan Carpenter and Brian Masney
- Rebased to next-20250829
- Link to v1: https://lore.kernel.org/r/20250812-clk-ssc-version1-v1-0-cef60f20d770@nxp.com

---
Peng Fan (6):
      dt-bindings: clock: Add spread spectrum definition
      clk: Introduce clk_hw_set_spread_spectrum
      clk: conf: Support assigned-clock-sscs
      clk: Add KUnit tests for assigned-clock-sscs
      clk: scmi: Introduce common header for SCMI clock interface
      clk: scmi: Add i.MX95 OEM extension support for SCMI clock driver

 drivers/clk/Makefile                               |   8 +-
 drivers/clk/clk-conf.c                             |  69 ++++++++++++
 drivers/clk/clk-scmi-oem.c                         | 103 ++++++++++++++++++
 drivers/clk/clk-scmi.c                             |  44 +++-----
 drivers/clk/clk-scmi.h                             |  51 +++++++++
 drivers/clk/clk.c                                  |  27 +++++
 drivers/clk/clk_test.c                             | 121 ++++++++++++++++++++-
 drivers/clk/kunit_clk_assigned_rates.h             |  10 ++
 drivers/clk/kunit_clk_assigned_rates_multiple.dtso |   6 +
 ...kunit_clk_assigned_rates_multiple_consumer.dtso |   6 +
 drivers/clk/kunit_clk_assigned_rates_one.dtso      |   3 +
 .../clk/kunit_clk_assigned_rates_one_consumer.dtso |   3 +
 .../clk/kunit_clk_assigned_rates_u64_multiple.dtso |   6 +
 ...t_clk_assigned_rates_u64_multiple_consumer.dtso |   6 +
 drivers/clk/kunit_clk_assigned_rates_u64_one.dtso  |   3 +
 .../kunit_clk_assigned_rates_u64_one_consumer.dtso |   3 +
 drivers/clk/kunit_clk_assigned_sscs_null.dtso      |  16 +++
 .../clk/kunit_clk_assigned_sscs_null_consumer.dtso |  20 ++++
 drivers/clk/kunit_clk_assigned_sscs_without.dtso   |  15 +++
 .../kunit_clk_assigned_sscs_without_consumer.dtso  |  19 ++++
 drivers/clk/kunit_clk_assigned_sscs_zero.dtso      |  12 ++
 .../clk/kunit_clk_assigned_sscs_zero_consumer.dtso |  16 +++
 include/dt-bindings/clock/clock.h                  |  14 +++
 include/linux/clk-provider.h                       |  31 ++++++
 24 files changed, 580 insertions(+), 32 deletions(-)
---
base-commit: ef68bf704646690aba5e81c2f7be8d6ef13d7ad8
change-id: 20251127-clk-ssc-v6-2-57658f944324

Best regards,
-- 
Peng Fan <peng.fan at nxp.com>