Commit bbc89a6e authored by Michael Wu's avatar Michael Wu Committed by Wolfram Sang
Browse files

dt-bindings: i2c: snps,designware-i2c: declare bus capacitance and clk freq optimized 



Since there are no registers controlling the hardware parameters
IC_CAP_LOADING and IC_CLK_FREQ_OPTIMIZATION, their values can only be
declared in the device tree.

snps,bus-capacitance-pf indicates the bus capacitance in picofarads (pF).
It affects the high and low pulse width of SCL line in high speed mode.
The legal values for this property are 100 and 400 only, and default
value is 100. This property corresponds to IC_CAP_LOADING.

snps,clk-freq-optimized indicates whether the hardware reduce its
internal clock frequency by reducing the internal latency required to
generate the high period and low period of SCL line. This property
corresponds to IC_CLK_FREQ_OPTIMIZATION.

The driver can calculate the high period count and low period count of
SCL line for high speed mode based on these two properties.

Signed-off-by: default avatarMichael Wu <michael.wu@kneron.us>
Reviewed-by: default avatarKrzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: default avatarAndi Shyti <andi.shyti@kernel.org>
Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
parent 4fb1b640

Documentation/devicetree/bindings/i2c/snps,designware-i2c.yaml

+18 −0
Original line number Diff line number Diff line
@@ -97,6 +97,22 @@ properties: 
      - const: tx

      - const: rx



  snps,bus-capacitance-pf:

    $ref: /schemas/types.yaml#/definitions/uint32

    description:

      This property indicates the bus capacitance in picofarads (pF).

      This value is used to compute the tHIGH and tLOW periods for high speed

      mode.

    enum: [100, 400]

    default: 100



  snps,clk-freq-optimized:

    description:

      This property indicates whether the hardware reduce its clock frequency

      by reducing the internal latency required to generate the high period and

      low period of SCL line.

    type: boolean



unevaluatedProperties: false



required:
@@ -121,6 +137,8 @@ examples: 
      i2c-sda-hold-time-ns = <300>;

      i2c-sda-falling-time-ns = <300>;

      i2c-scl-falling-time-ns = <300>;

      snps,bus-capacitance-pf = <400>;

      snps,clk-freq-optimized;

    };

  - |

    i2c@2000 {