[PATCH v2 0/4] pwm: meson: make full use of common clock framework

Heiner Kallweit
2023-04-11T19:22:28Z

Newer versions of the PWM block use a core clock with external mux,
divider, and gate. These components either don't exist any longer in
the PWM block, or they are bypassed.
To minimize needed changes for supporting the new version, the internal
divider and gate should be handled by CCF too.

I didn't see a good way to split the patch, therefore it's somewhat
bigger. What it does:

- The internal mux is handled by CCF already. Register also internal
divider and gate with CCF, so that we have one representation of the
input clock: [mux] parent of [divider] parent of [gate]

- Now that CCF selects an appropriate mux parent, we don't need the
DT-provided default parent any longer. Accordingly we can also omit
setting the mux parent directly in the driver.

- Instead of manually handling the pre-div divider value, let CCF
set the input clock. Targeted input clock frequency is
0xffff * 1/period for best precision.

- For the "inverted pwm disabled" scenario target an input clock
frequency of 1GHz. This ensures that the remaining low pulses
have minimum length.

I don't have hw with the old PWM block, therefore I couldn't test this
patch. With the not yet included extension for the new PWM block
(channel->clock directly coming from get_clk(external_clk)) I didn't
notice any problem. My system uses PWM for the CPU voltage regulator
and for the SDIO 32kHz clock.

Note: The clock gate in the old PWM block is permanently disabled.
This seems to indicate that it's not used by the new PWM block.

Changes to RFT/RFC version:
- use parent_hws instead of parent_names for div/gate clock
- use devm_clk_hw_register where the struct clk * returned by
devm_clk_register isn't needed

v2:
- add patch 1
- add patch 3
- switch to using clk_parent_data in all relevant places

Heiner Kallweit (4):
pwm: meson: switch to using struct clk_parent_data for mux parents
pwm: meson: don't use hdmi/video clock as mux parent
pwm: meson: change clk/pwm gate from mask to bit
pwm: meson: make full use of common clock framework

drivers/pwm/pwm-meson.c | 194 +++++++++++++++++++++-------------------
1 file changed, 101 insertions(+), 93 deletions(-)

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2.40.0