Re: [PATCH v4 0/4] Introduce Allwinner H616 PWM controller

[Richard GENOUD <richard.genoud@bootlin.com>]

Le 05/03/2026 à 10:19, Richard Genoud a écrit :
> Allwinner H616 PWM controller is quite different from the A10 one.
> 
> It can drive 6 PWM channels, and like for the A10, each channel has a
> bypass that permits to output a clock, bypassing the PWM logic, when
> enabled.
> 
> But, the channels are paired 2 by 2, sharing a first set of
> MUX/prescaler/gate.
> Then, for each channel, there's another prescaler (that will be bypassed
> if the bypass is enabled for this channel).
> 
> It looks like that:
>              _____      ______      ________
> OSC24M --->|     |    |      |    |        |
> APB1 ----->| Mux |--->| Gate |--->| /div_m |-----> PWM_clock_src_xy
>             |_____|    |______|    |________|
>                            ________
>                           |        |
>                        +->| /div_k |---> PWM_clock_x
>                        |  |________|
>                        |    ______
>                        |   |      |
>                        +-->| Gate |----> PWM_bypass_clock_x
>                        |   |______|
> PWM_clock_src_xy -----+   ________
>                        |  |        |
>                        +->| /div_k |---> PWM_clock_y
>                        |  |________|
>                        |    ______
>                        |   |      |
>                        +-->| Gate |----> PWM_bypass_clock_y
>                            |______|
> 
> Where xy can be 0/1, 2/3, 4/5
> 
> PWM_clock_x/y serve for the PWM purpose.
> PWM_bypass_clock_x/y serve for the clock-provider purpose.
> The common clock framework has been used to manage those clocks.
> 
> This PWM driver serves as a clock-provider for PWM_bypass_clocks.
> This is needed for example by the embedded AC300 PHY which clock comes
> from PMW5 pin (PB12).
> 
> Usually, to get a clock from a PWM driver, we use the pwm-clock driver
> so that the PWM driver doesn't need to be a clk-provider itself.
> While this works in most cases, here it just doesn't.
> That's because the pwm-clock request a period from the PWM driver,
> without any clue that it actually wants a clock at a specific frequency,
> and not a PWM signal with duty cycle capability.
> So, the PWM driver doesn't know if it can use the bypass or not, it
> doesn't even have the real accurate frequency information (23809524 Hz
> instead of 24MHz) because PWM drivers only deal with periods.
> 
> With pwm-clock, we loose a precious information along the way (that we
> actually want a clock and not a PWM signal).
> That's ok with simple PWM drivers that don't have multiple input clocks,
> but in this case, without this information, we can't know for sure which
> clock to use.
> And here, for instance, if we ask for a 24MHz clock, pwm-clock will
> requests 42ns (assigned-clocks doesn't help for that matter). The logic
> is to select the highest clock (100MHz) with no prescaler and a duty
> cycle value of 2/4 => we have 25MHz instead of 24MHz.
> And that's a perfectly fine choice for a PMW, because we still can
> change the duty cycle in the range [0-4]/4.
> But obviously for a clock, we don't care about the duty cycle, but more
> about the clock accuracy.
> 
> And actually, this PWM is really a PWM AND a real clock when the bypass
> is set.
> 
> This series is based onto v6.19-rc4
> 
> NB: checkpatch is not happy with patch 2, but it's a false positive.
> It doesn't detect that PWM_XY_SRC_MUX/GATE/DIV are structures, but as
> it's more readable like that, I prefer keeping it that way.
> 
> NB2: for geopolitical reasons, I didn't re-use the old series that Paul
> was referring to.
> 

Hi Uwe, do you plan to grab this series or does it needs some further 
reviews?

Regards,
Richard

> Changes since v3:
> - gather Acked-by/Tested-by
> - fix cast from pointer to integer of different size (kernel test robot
>    with arc platform)
> - add devm_action for clk_hw_unregister_composite as suggested by Philipp
> - remove now unused pwm_remove as suggested by Philipp
> 
> Changes since v2:
> - use U32_MAX instead of defining UINT32_MAX
> - add a comment on U32_MAX usage in clk_round_rate()
> - change clk_table_div_m (use macros)
> - fix formatting (double space, superfluous comma, extra line feed)
> - fix the parent clock order
> - simplify code by using scoped_guard()
> - add missing const in to_h616_pwm_chip() and rename to
> h616_pwm_from_chip()
> - add/remove missing/superflous error messages
> - rename cnt->period_ticks, duty_cnt->duty_ticks
> - fix PWM_PERIOD_MAX
> - add .remove() callback
> - fix DIV_ROUND_CLOSEST_ULL->DIV_ROUND_UP_ULL
> - add H616_ prefix
> - protect _reg in macros
> - switch to waveforms instead of apply/get_state
> - shrink struct h616_pwm_channel
> - rebase on v6.19-rc4
> 
> Changes since v1:
> - rebase onto v6.19-rc1
> - add missing headers
> - remove MODULE_ALIAS (suggested by Krzysztof)
> - use sun4i-pwm binding instead of creating a new one (suggested by Krzysztof)
> - retrieve the parent clocks from the devicetree
> - switch num_parents to unsigned int
> 
> Richard Genoud (4):
>    dt-bindings: pwm: allwinner: add h616 pwm compatible
>    pwm: sun50i: Add H616 PWM support
>    arm64: dts: allwinner: h616: add PWM controller
>    MAINTAINERS: Add entry on Allwinner H616 PWM driver
> 
>   .../bindings/pwm/allwinner,sun4i-a10-pwm.yaml |  19 +-
>   MAINTAINERS                                   |   5 +
>   .../arm64/boot/dts/allwinner/sun50i-h616.dtsi |  47 +
>   drivers/pwm/Kconfig                           |  12 +
>   drivers/pwm/Makefile                          |   1 +
>   drivers/pwm/pwm-sun50i-h616.c                 | 936 ++++++++++++++++++
>   6 files changed, 1019 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/pwm/pwm-sun50i-h616.c
> 
> 
> base-commit: 11439c4635edd669ae435eec308f4ab8a0804808