[PATCH v8 0/3] Update designware pwm driver

[dongxuyang@eswincomputing.com]

From: Xuyang Dong <dongxuyang@eswincomputing.com>

There is already a patch [1] for the DesignWare PWM driver,
which is posted by Ben and still under review.
Based on this patch, this series is a continuation of [1]
to add support for IP versions 2.11a and later, which
includes support for "Pulse Width Modulation with 0%
and 100% Duty Cycle".

Supported chips:
ESWIN EIC7700 series SoC.

Test:
Tested this patch on the Sifive HiFive Premier P550 (which uses the EIC7700
SoC).

[1] https://lore.kernel.org/lkml/20230907161242.67190-1-ben.dooks@codethink.co.uk/

Updates:
  Changes in v8:
  - YAML:
    - Split the v7 binding into two patches.
      Patch 1 explains why to add the resets property.
      Patch 2 adds the eswin compatible string and specified reset.
  - Driver:
    - Use mul_u64_u64_div_u64() to safely scale the values and avoid
      64-bit multiplication overflow in __dwc_pwm_configure_timer()
      and dwc_pwm_get_state().
      Add the include for linux/math64.h (Sashiko review of v7).
    - Keep the current usage of pwm->args.polarity until a better solution
      is available.
    - Use pm_runtime_resume_and_get() in dwc_pwm_get_state() instead of
      pm_runtime_get_sync(), so that register access is skipped if the
      device fails to resume (Sashiko review of v7).
    - Replace devm_pwmchip_add() with pwmchip_add() and move it after
      pm_runtime_enable(), so that the PWM chip is registered only after
      runtime PM has been fully initialized (Sashiko review of v7).
    - Remove the reset_assert label and reset_control_assert()
      (Sashiko review of v7).
    - Remove the pm_runtime_status_suspended() check and unconditionally
      use pm_runtime_get_sync() instead (Sashiko review of v7).
    - Remove  the pwm_en flag, but keep the pm_runtime_put_noidle() call
      (Sashiko review of v7; see email for explanation)
    - Use pm_runtime_status_suspended() to check the runtime PM status.
      If the device is not suspended (i.e., active), call
      clk_disable_unprepare(). If it is suspended, skip this block
      (Sashiko review of v7).
    - Use an explicit pwmchip_remove() as the first step of .remove(),
      instead of relying on devm_pwmchip_add() to unregister the chip
      after .remove() returns. This prevents the hardware teardown that
      follows from racing against a still-registered chip
      (Sashiko review of v7).
    - Add a check for dwc->rst before asserting reset in the remove path
      (Sashiko review of v7).
    - Drop the return value check from pm_runtime_put_sync()
      (Sashiko review of v7).

  - Link to v7: https://lore.kernel.org/all/20260605082242.1541-1-dongxuyang@eswincomputing.com/

  Changes in v7:
  - YAML:
    - Dropped Conor's Acked-by due to significant schema changes.
    - Rename patch 1 from "dt-bindings: pwm: dwc: add optional reset" to
      "dt-bindings: pwm: dwc: Add eswin compatible and resets property".
    - Update the commit message to explain why the EIC7700 supports only
      one reset.
    - Add constraints 'minItems: 1' and 'maxItems: 1' for the 'resets'
      property of eswin,eic7700-pwm.
    - Add an example for eswin,eic7700-pwm.

  - Link to v6: https://lore.kernel.org/all/20260424094529.1691-1-dongxuyang@eswincomputing.com/

  Changes in v6:
  - YAML:
    - Drop properties resets and its items description for eswin,eic7700-pwm.

  - Link to v5: https://lore.kernel.org/all/20260423083644.1168-1-dongxuyang@eswincomputing.com/

  Changes in v5:
  - YAML:
    - Add 'eswin,eic7700-pwm' compatible string.
    - Add the items description for the resets property and set minItems to 1.
    - Require resets property with exactly 1 reset for eswin,eic7700-pwm compatible.
  - Driver:
    - Add support for 'eswin,eic7700-pwm' compatible.
    - Add structure dwc_pwm_plat_data to manage the API for obtaining resets.

  - Link to v4: https://lore.kernel.org/all/20260415094908.1539-1-dongxuyang@eswincomputing.com/

  Changes in v4:
  - YAML:
    - Change maxItems from 1 to 2. As there is a corresponding reset signal
      for each clock domain, the effective maxItems of the resets property
      is set to 2.
    - Update the YAML commit message to describe the hardware.
  - Driver:
    - Replace devm_reset_control_get_optional_exclusive() with
      devm_reset_control_array_get_optional_exclusive(). Since the number
      of reset signals has increased from one to two, we need to use the
      array API to acquire them.

  - Link to v3: https://lore.kernel.org/all/20260402091718.1608-1-dongxuyang@eswincomputing.com/

  Changes in v3:
  - YAML:
    - Added a clear justification for the optional resets property. It is
      required to support proper controller initialization when no PWM
      channel is active at boot time, while allowing the driver to skip
      reset deassertion if any channel is already enabled.
  - Driver:
    - Update the boundary value check of tmp in __dwc_pwm_configure_timer()
      for DWC_TIM_CTRL_0N100PWM_EN.
    - Replace 'sizeof(struct dwc_pwm_drvdata)' with
      'struct_size(data, chips, 1)'.
    - Drop devm_clk_get_enabled() in favor of devm_clk_get() with explicit
      clk_prepare_enable() and clk_disable_unprepare() allowing runtime PM
      to manage clock state.
    - Replace devm_reset_control_get_optional_exclusive_deasserted() with
      devm_reset_control_get_optional_exclusive() and issue a full reset via
      reset_control_reset() only when no PWM channel is active at probe time.
    - Detect bootloader-enabled PWM channels by reading the enable bit, and
      initialize runtime PM as active for those channels by calling
      pm_runtime_set_active() and pm_runtime_get_noresume().
    - Remove autosuspend as it is not required for this driver.
    - Use explicit pm_runtime_enable() and pm_runtime_disable() instead of
      the managed devm_pm_runtime_enable() variant to ensure correct cleanup.
    - On device removal, recheck the channel enable status. If any channel
      remains active, call pm_runtime_put_noidle() before disabling clocks
      via clk_disable_unprepare().
      Resume device before register access during removal if it is runtime
      suspended, and re-suspend it afterward.
    - If device is suspended, resume it before register access during system
      resume/suspend.
    - Use pm_ptr() instead of pm_sleep_ptr() for correct PM operation.

  - Link to v2: https://lore.kernel.org/all/20260306093000.2065-1-dongxuyang@eswincomputing.com/

  Changes in v2:
  - YAML:
    - Remove eswin,eic7700-pwm.yaml. Use snps,dw-apb-timers-pwm2.yaml.
      The description in snps,dw-apb-timers-pwm2.yaml is better.
    - Add the resets property as optional, as defined in the databook.
    - Remove snps,pwm-full-range-enable as no additional property is needed.
  - Driver:
    - Change the file from pwm-dwc-eic7700.c to pwm-dwc-of.c from [1].
    - Define DWC_TIM_VERSION_ID_2_11A 2.11a as the baseline version.
    - Enable the 0% and 100% duty cycle mode by setting dwc->feature if
      the version read from the TIMERS_COMP_VERSION register is later
      than or equal to DWC_TIM_VERSION_ID_2_11A.
    - Use the DIV_ROUND_UP_ULL() to calculate width in the .apply and
      .get_state.
    - Additionally, Power Management (PM) support has been added to the
      pwm-dwc-of.c driver.
    - Drop the headers that are not used.
    - Use devm_clk_get_enabled() instead of devm_clk_get().
    - Drop of_match_ptr.
    - Fix build error with 1ULL << 32.
      Reported-by: kernel test robot <lkp@intel.com>
      Closes: https://lore.kernel.org/oe-kbuild-all/202512061720.j31AsgM7-lkp@intel.com/

  - Link to v1: https://lore.kernel.org/all/20251205090411.1388-1-dongxuyang@eswincomputing.com/
  - Link to v9: https://lore.kernel.org/lkml/20230907161242.67190-1-ben.dooks@codethink.co.uk/

Xuyang Dong (3):
  dt-bindings: pwm: dwc: Document optional resets property
  dt-bindings: pwm: dwc: Add eswin compatible
  pwm: dwc: add of/platform support

 .../bindings/pwm/snps,dw-apb-timers-pwm2.yaml |  37 +-
 drivers/pwm/Kconfig                           |  10 +
 drivers/pwm/Makefile                          |   1 +
 drivers/pwm/pwm-dwc-core.c                    | 103 ++++--
 drivers/pwm/pwm-dwc-of.c                      | 346 ++++++++++++++++++
 drivers/pwm/pwm-dwc.h                         |  25 +-
 6 files changed, 488 insertions(+), 34 deletions(-)
 create mode 100644 drivers/pwm/pwm-dwc-of.c

--
2.34.1