Re: [PATCH 2/2] regulator: qcom_usb_vbus: add support for qcom,pm4125-vbus-reg

[Rakesh Kota]

On Wed, May 20, 2026 at 11:51:49AM +0200, Konrad Dybcio wrote:
> On 5/20/26 11:07 AM, Rakesh Kota wrote:
> > The PM4125 PMIC uses a different register layout for USB VBUS control
> > compared to PM8150B. On PM4125, CMD_OTG is at offset 0x50, OTG_CFG is
> > at 0x56, and offset 0x52 is a 2-bit VBOOST voltage selector rather than
> > a current-limit selector.
> > 
> > Introduce per-compatible regulator descriptor data to accommodate these
> > differences. This keeps the existing PM8150B current-limit logic intact
> > while adding a dedicated voltage-selector path for PM4125.
> > 
> > Signed-off-by: Rakesh Kota <rakesh.kota@xxxxxxxxxxxxxxxx>
> > ---
> >  drivers/regulator/qcom_usb_vbus-regulator.c | 102 ++++++++++++++++++++++++----
> >  1 file changed, 88 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/regulator/qcom_usb_vbus-regulator.c b/drivers/regulator/qcom_usb_vbus-regulator.c
> > index cd94ed67621fee9f6d7a0327054db0ebab6cc7ee..3d425452a0b35b35c4b454f84eb28e87cc8ba4f8 100644
> > --- a/drivers/regulator/qcom_usb_vbus-regulator.c
> > +++ b/drivers/regulator/qcom_usb_vbus-regulator.c
> > @@ -20,10 +20,35 @@
> >  #define OTG_CFG				0x53
> >  #define OTG_EN_SRC_CFG			BIT(1)
> >  
> > +#define PM4125_CMD_OTG			0x50
> 
> This register is named differently
Ok, i will update name to PM4125_VBOOST_EN in next version.
> 
> > +#define PM4125_VBOOST_CFG		0x52
> > +#define PM4125_VBOOST_CFG_MASK		GENMASK(1, 0)
> > +#define PM4125_OTG_CFG			0x56
> 
> And so is this one
update name to PM4125_VBOOST_CFG in next version
> 
> 
> > +#define PM4125_OTG_EN_SRC_CFG          BIT(0)
> > +
> > +struct qcom_usb_vbus_reg_data {
> > +	u16 cmd_otg;
> > +	u16 otg_cfg;
> > +	u8  otg_en_src_cfg;
> > +	u16 csel_reg;
> > +	u8 csel_mask;
> > +	const unsigned int *curr_table;
> > +	unsigned int n_current_limits;
> > +	u16 vsel_reg;
> > +	u8 vsel_mask;
> > +	const unsigned int *volt_table;
> > +	unsigned int n_voltages;
> > +	const struct regulator_ops *ops;
> > +};
> 
> And because they're so different, keeping them in a single driver starts to
> look a little odd

You are right, they differ in control mechanism — one uses current
control and the other uses voltage control for VBUS in host mode.
Since the functional purpose is the same (VBUS regulation in host
mode), I felt a single driver made sense to avoid code duplication.

But open to suggestions — should I split this into separate drivers
or is there a better way to handle this cleanly?
> 
> > +
> >  static const unsigned int curr_table[] = {
> >  	500000, 1000000, 1500000, 2000000, 2500000, 3000000,
> >  };
> 
> And I think there's current-limiting on this PMIC too, except in a differnt
> peripheral (@1300)
> 
The @1300 peripheral is for ICL (Input Current Limit) in device mode
charging — not for host mode VBUS regulation.

Could you share the register you're referring to for further clarity?

regards
Rakesh
> Konrad