[PATCH v8 0/3] Change PWM-controlled LED pin active mode and algorithm

[Nylon Chen]

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.

Updated patches: 3
New patches: 0
Unchanged patches: 0

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

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 (3):
  riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's
    active-low properties
  pwm: sifive: change the PWM controlled LED algorithm
  pwm: sifive: Fix the error in the idempotent test within the
    pwm_apply_state_debug function

 arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 12 ++++--------
 arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts | 12 ++++--------
 drivers/pwm/pwm-sifive.c                            |  9 +++++----
 3 files changed, 13 insertions(+), 20 deletions(-)

-- 
2.42.0