In commit 35eba185fd1a ("i2c: designware: Calculate SCL timing parameters for
High Speed Mode") hs_hcnt and hs_lcnt are computed based on fixed tHIGH = 160
and tLOW = 320. However, the set of these fixed values only applies to the
combination of hardware parameters "IC_CAP_LOADING = 400pF" and
"IC_FREQ_OPTIMIZATION = 1". Outside of this combination, SCL frequency may not
reach 3.4 MHz if hs_hcnt and hs_lcnt are both computed using these two fixed
values.

Since there are no any registers controlling these two hardware parameters,
their values can only be declared through the device tree.

v3:
- add vendor prefix on new property name
- read new properties in i2c_dw_fw_parse_and_configure() directly
- in i2c_dw_set_timings_master() check dev->bus_capacitance_pf and then decide
  t_high and t_low

v2:
- provide more hardware information in dt-bindings
- rename "bus-loading" to "bus-capacitance-pf"
- call new i2c_dw_fw_parse_hw_params() in i2c_dw_fw_parse_and_configure() to
  parse hardware parameters from the device tree.

Michael Wu (2):
  dt-bindings: i2c: snps,designware-i2c: declare bus capacitance and clk
    freq optimized
  i2c: dwsignware: determine HS tHIGH and tLOW based on HW parameters

 .../bindings/i2c/snps,designware-i2c.yaml     | 24 +++++++++++++++++++
 drivers/i2c/busses/i2c-designware-common.c    |  5 ++++
 drivers/i2c/busses/i2c-designware-core.h      |  5 ++++
 drivers/i2c/busses/i2c-designware-master.c    | 23 ++++++++++++++++--
 4 files changed, 55 insertions(+), 2 deletions(-)

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2.43.0