[PATCH v5 0/2] Add divisor computation feature for sdm845 gp clocks

[Dzmitry Sankouski <dsankouski@gmail.com>]

SDM845 has "General Purpose" clocks that can be muxed to
SoC pins to clock various external devices.
Those clocks may be used as e.g. PWM sources for external peripherals.
    
GPCLK can in theory have arbitrary value depending on the use case, so
the concept of frequency tables, used in rcg2 clock driver, is not
efficient, because it allows only defined frequencies.
    
Introduce clk_rcg2_gp_ops, which automatically calculate clock
mnd values for arbitrary clock rate. The calculation done as follows:
- upon determine rate request, we calculate m/n/pre_div as follows:
  - find parent(from our client's assigned-clock-parent) rate
  - find scaled rates by dividing rates on its greatest common divisor
  - assign requested scaled rate to m
  - factorize scaled parent rate, put multipliers to n till max value
    (determined by mnd_width)
- validate calculated values with *_width:
  - if doesn't fit, delete divisor and multiplier by 2 until fit
- return determined rate
    
Limitations:
- The driver doesn't select a parent clock (it may be selected by client
  in device tree with assigned-clocks, assigned-clock-parents properties)

Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
---
Changes in v5:
- Split patchset per subsystem
- Link to v4: https://lore.kernel.org/r/20240913-starqltechn_integration_upstream-v4-0-2d2efd5c5877@gmail.com

Changes in v4:
- Replace gcc-845 freq_tbl frequencies patch with new approach,
  based on automatic m/n/pre_div value generation
- Link to v3: https://lore.kernel.org/r/20240618-starqltechn_integration_upstream-v3-0-e3f6662017ac@gmail.com

---
Dzmitry Sankouski (2):
      clk: qcom: clk-rcg2: document calc_rate function
      gcc-sdm845: Add general purpose clock ops

 drivers/clk/qcom/clk-rcg.h    |   1 +
 drivers/clk/qcom/clk-rcg2.c   | 201 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 drivers/clk/qcom/gcc-sdm845.c |  11 ++----
 3 files changed, 198 insertions(+), 15 deletions(-)
---
base-commit: 92fc9636d1471b7f68bfee70c776f7f77e747b97
change-id: 20240617-starqltechn_integration_upstream-bc86850b2fe3

Best regards,
-- 
Dzmitry Sankouski <dsankouski@gmail.com>