Unverified Commit b54a27d8 authored by Matti Vaittinen's avatar Matti Vaittinen Committed by Mark Brown
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regulator: BD71847 support commonly used feedback connection 



The BD71847 buck output voltages are in a few cases scaled using external
connection which adds a pull-up to regulator feedback pin. This connection
will adjust output voltage from regulator in a deterministic way.

Add support for describing this HW connection so that driver can adjust
voltage ranges accordingly.

Signed-off-by: default avatarMatti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/9b6b3d8233071d478f7d1e93b498f5a2141941e6.1604994184.git.matti.vaittinen@fi.rohmeurope.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 1e908b24

Documentation/devicetree/bindings/regulator/rohm,bd71847-regulator.yaml

+49 −0
Original line number Diff line number Diff line
@@ -99,6 +99,55 @@ patternProperties: 
          Enable/Disable control of this regulator must be left to the

          PMIC hardware state machine.

        type: boolean



      # Setups where regulator (especially the buck8) output voltage is scaled

      # by adding external connection where some other regulator output is

      # connected to feedback-pin (over suitable resistors) is getting popular

      # amongst users of BD71837. (This allows for example scaling down the

      # buck8 voltages to suit lover GPU voltages for projects where buck8 is

      # (ab)used to supply power for GPU.

      #

      # So we allow describing this external connection from DT and scale the

      # voltages accordingly. This is what the connection should look like:

      #

      # |---------------|

      # |       buck 8  |-------+----->Vout

      # |               |       |

      # |---------------|       |

      #        |                |

      #        |                |

      #        +-------+--R2----+

      #                |

      #                R1

      #                |

      #        V FB-pull-up

      #

      # Here the buck output is sifted according to formula:

      #

      # Vout_o = Vo - (Vpu - Vo)*R2/R1

      # Linear_step = step_orig*(R1+R2)/R1

      #

      # where:

      # Vout_o is adjusted voltage output at vsel reg value 0

      # Vo is original voltage output at vsel reg value 0

      # Vpu is the pull-up voltage V FB-pull-up in the picture

      # R1 and R2 are resistor values.



      rohm,fb-pull-up-microvolt:

        description:

          Feedback-pin has pull-up connection to adjust voltage range. This is

          the used pull-up voltage before R1.



      rohm,feedback-pull-up-r1-ohms:

        description:

          Feedback-pin has pull-up connection to adjust voltage range. This is

          the used R1 resistor.



      rohm,feedback-pull-up-r2-ohms:

        description:

          Feedback-pin has pull-up connection to adjust voltage range. This is

          the used R2 resistor.



    required:

      - regulator-name