From b54a27d8109fc8f18cec3e0663f8e81ea727e3c6 Mon Sep 17 00:00:00 2001 From: Matti Vaittinen Date: Tue, 10 Nov 2020 10:19:58 +0200 Subject: [PATCH] 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: Matti Vaittinen Link: https://lore.kernel.org/r/9b6b3d8233071d478f7d1e93b498f5a2141941e6.1604994184.git.matti.vaittinen@fi.rohmeurope.com Signed-off-by: Mark Brown --- .../regulator/rohm,bd71847-regulator.yaml | 49 +++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/Documentation/devicetree/bindings/regulator/rohm,bd71847-regulator.yaml b/Documentation/devicetree/bindings/regulator/rohm,bd71847-regulator.yaml index eeac32cd15d6..a1b806373853 100644 --- a/Documentation/devicetree/bindings/regulator/rohm,bd71847-regulator.yaml +++ b/Documentation/devicetree/bindings/regulator/rohm,bd71847-regulator.yaml @@ -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