[RFC PATCH 4/5] mfd: axp20x: Support tri-phase setup

[Andre Przywara <andre.przywara@arm.com>]

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