According to the circuit diagram of User LEDs - RGB described in the
manual hifive-unleashed-a00.pdf[0] and hifive-unmatched-schematics-v3.pdf[1].

The behavior of PWM is acitve-high.

According to the descriptionof PWM for pwmcmp in SiFive FU740-C000 Manual[2].

The pwm algorithm is (PW) pulse active time  = (D) duty * (T) period.
The `frac` variable is pulse "inactive" time so we need to invert it.

So this patchset removes active-low in DTS and adds reverse logic to the driver.

Links:
- [0]: https://sifive.cdn.prismic.io/sifive/c52a8e32-05ce-4aaf-95c8-7bf8453f8698_hifive-unleashed-a00-schematics-1.pdf
- [1]: https://sifive.cdn.prismic.io/sifive/6a06d6c0-6e66-49b5-8e9e-e68ce76f4192_hifive-unmatched-schematics-v3.pdf
- [2]: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf

Updated patches: 1
New patches: 0
Unchanged patches: 4

Changed in v14:
 - Change `frac` from `u32` to `u64` and cast the constant in `min()` to
   `u64`  so that `do_div(frac, state->period)` no longer triggers type-mismatch

Changed in v13:
 - Fix syntax error: Added missing closing parenthesis in do_div()
   function call.

Changed in v12:
 - Replace division with do_div() to fix __udivdi3 modpost error.

Changed in v11:
 - Fix rounding consistency in apply() and get_state()
 - Add code comments to help clarify Reference Manual errors.

Changed in v10:
 - Add 'inactive' variable in apply() to match pwm_sifive_get_state()
   style
 - Update comment about hardware limitation - it cannot generate 0% duty
   cycle rather than 100% duty cycle

Changed in v9:
 - Fix commit message to adhere to 75 columns rule.
 - Update commit message's subject.
 - Add a variable for inactive logic.

Changed in v8:
 - Fix Signed-off-by and Co-developed-by typo.

Changed in v7:
 - Remove active-low strings from hifive-unleashed-a00.dts file.

Changed in v6:
 - Separate the idempotent test bug fixes into a new patch.
 - Move the reversing the duty before the line checking
   state->enabled.
 - Fix the algorithm and change it to take the minimum value first and
   then reverse it.

Changed in v5:
 - Add the updates to the PWM algorithm based on version 2 back in.
 - Replace div64_ul with DIV_ROUND_UP_ULL to correct the error in the
   period value of the idempotent test in pwm_apply_state_debug.

Changed in v4:
 - Remove previous updates to the PWM algorithm.

Changed in v3:
 - Convert the reference link to standard link.
 - Move the inverted function before taking the minimum value.
 - Change polarity check condition(high and low).
 - Pick the biggest period length possible that is not bigger than the
   requested period.

Changed in v2:
 - Convert the reference link to standard link.
 - Fix typo: s/sifive unmatched:/sifive: unmatched:/.
 - Remove active-low from hifive-unleashed-a00.dts.
 - Include this reference link in the dts and pwm commit messages.

Nylon Chen (5):
  riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's
    active-low properties
  pwm: sifive: change the PWM algorithm
  pwm: sifive: Fix the error in the idempotent test within the
    pwm_apply_state_debug function
  pwm: sifive: Fix rounding issues in apply and get_state functions
  pwm: sifive: clarify inverted compare logic in comments

 .../boot/dts/sifive/hifive-unleashed-a00.dts  | 12 ++---
 .../boot/dts/sifive/hifive-unmatched-a00.dts  | 12 ++---
 drivers/pwm/pwm-sifive.c                      | 52 ++++++++++++++-----
 3 files changed, 47 insertions(+), 29 deletions(-)

-- 
2.34.1

Hello,

patches 1 and 2 ideally go in together, right? @Conor, does your Ack
mean that you're OK with me taking the dts change via my pwm tree?

On Fri, May 09, 2025 at 05:52:29PM +0800, Nylon Chen wrote:
> Nylon Chen (5):
>   riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's
>     active-low properties
>   pwm: sifive: change the PWM algorithm
>   pwm: sifive: Fix the error in the idempotent test within the
>     pwm_apply_state_debug function
>   pwm: sifive: Fix rounding issues in apply and get_state functions
>   pwm: sifive: clarify inverted compare logic in comments

The objective of patches #3 and #4 is the same, right? Both prevent that
.apply ∘ .get_state is idempotent, right?

And I'd also squash patches #2 and #5 to have the comments updated
together with the respective code changes.

I think the algorithm implemented in this driver is more complicated
than it should be, but this is not this series's fault, so I tend to
apply it with the above mentioned squashes.

Best regards
Uwe

On Wed, May 28, 2025 at 12:21:45PM +0200, Uwe Kleine-König wrote:
> Hello,
> 
> patches 1 and 2 ideally go in together, right? @Conor, does your Ack
> mean that you're OK with me taking the dts change via my pwm tree?

That's exactly what an ack from me means, yes.