Of the PMICs that support multi-phased regulators, all but one just
support a dual-phase setup, with exactly two regulators tied together.
This allows for a simple data model, since just two is somewhat of a
special case.

However there is the AXP806, which supports a triple-phase setup, that is
also used on at least one board: the Cubieboard 4, where DCDC-A+B+C
together supply the Cortex-A15 CPU cluster.
Since this is just one case, and a fairly old one now, let's not boil
the ocean by coming up with a complex data structure that allows
describing arbitrary combinations, but instead handle this as a special
case. This is supported by the fact, that the AXP806 only supports two
specific setups: DCDC-A+B or DCDC-A+B+C, but nothing else.

Add a function that checks for the regulators on this PMIC, and handle
the two cases, plus the one without any poly-phasing.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 drivers/regulator/axp20x-regulator.c | 45 ++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/drivers/regulator/axp20x-regulator.c b/drivers/regulator/axp20x-regulator.c
index e3acc4635a0ed..9dd666f228b1e 100644
--- a/drivers/regulator/axp20x-regulator.c
+++ b/drivers/regulator/axp20x-regulator.c
@@ -1569,6 +1569,39 @@ static int axp20x_find_polyphased_reg(const struct regulator_desc *regs,
 	return -ENODEV;
 }
 
+static int axp20x_handle_triphase(struct axp20x_dev *axp20x,
+				  int reg1, int reg2, int reg3)
+{
+	if (axp20x->variant == AXP806_ID && reg1 == AXP806_DCDCA) {
+		/* no other regulator listed: single phase setup */
+		if (reg2 == -ENOENT && reg3 == -ENOENT) {
+			regmap_update_bits(axp20x->regmap,
+					   AXP806_DCDC_MODE_CTRL2,
+					   AXP806_DCDCABC_POLYPHASE_MASK, 0);
+			return 0;
+		}
+		/* only regulator listed is DCDC-B: dual phase setup */
+		if (reg2 == AXP806_DCDCB && reg3 == -ENOENT) {
+			regmap_update_bits(axp20x->regmap,
+					   AXP806_DCDC_MODE_CTRL2,
+					   AXP806_DCDCABC_POLYPHASE_MASK,
+					   AXP806_DCDCAB_POLYPHASE_DUAL);
+			return 0;
+		}
+		/* both DCDC-B+C regulators listed: tri phase setup */
+		if ((reg2 == AXP806_DCDCB && reg3 == AXP806_DCDCC) ||
+		    (reg2 == AXP806_DCDCC && reg3 == AXP806_DCDCB)) {
+			regmap_update_bits(axp20x->regmap,
+					   AXP806_DCDC_MODE_CTRL2,
+					   AXP806_DCDCABC_POLYPHASE_MASK,
+					   AXP806_DCDCABC_POLYPHASE_TRI);
+			return 0;
+		}
+	}
+
+	return 0;
+}
+
 static int axp20x_parse_polyphase(struct axp20x_dev *axp20x, int primary_reg_id,
 				  const struct regulator_desc *regs,
 				  int nregulators, const struct device_node *np)
@@ -1610,6 +1643,18 @@ static int axp20x_parse_polyphase(struct axp20x_dev *axp20x, int primary_reg_id,
 		}
 	}
 
+	/* Special handling for the AXP806 DCDC-A/B/C tri-phase regulator. */
+	if (axp20x->variant == AXP806_ID && primary_reg_id == AXP806_DCDCA) {
+		int reg3_id;
+
+		reg3_id = axp20x_find_polyphased_reg(regs, nregulators, np, 1);
+		if (reg3_id < 0 && reg3_id != -ENOENT)
+			return reg_id;
+
+		return axp20x_handle_triphase(axp20x, primary_reg_id,
+					      reg_id, reg3_id);
+	}
+
 	return 0;
 }
 
-- 
2.46.4

On Fri, Sep 19, 2025 at 01:00:19AM +0100, Andre Przywara wrote:
> Of the PMICs that support multi-phased regulators, all but one just
> support a dual-phase setup, with exactly two regulators tied together.
> This allows for a simple data model, since just two is somewhat of a
> special case.

Acked-by: Mark Brown <broonie@kernel.org>

On Fri, Sep 19, 2025 at 01:00:19AM +0100, Andre Przywara wrote:
> Of the PMICs that support multi-phased regulators, all but one just
> support a dual-phase setup, with exactly two regulators tied together.
> This allows for a simple data model, since just two is somewhat of a
> special case.

Oh, and:

Please submit patches using subject lines reflecting the style for the
subsystem, this makes it easier for people to identify relevant patches.
Look at what existing commits in the area you're changing are doing and
make sure your subject lines visually resemble what they're doing.
There's no need to resubmit to fix this alone.