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 <matti.vaittinen@xxxxxxxxxxxxxxxxx>
---
.../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
--
2.21.3
--
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND
~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =]
