[RFC,5/8] regulator: anatop: fix min dropout for bypass mode
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Message ID cd944a7223cfe68788c299082a5f262e8bea2136.1490199005.git.leonard.crestez@nxp.com
State RFC, archived
Headers show

Commit Message

Leonard Crestez March 22, 2017, 4:53 p.m. UTC
From: Irina Tirdea <irina.tirdea@nxp.com>

In bypass mode, the anatop digital regulators do not have any minimum
dropout value (the input voltage is equal to the output voltage according
to documentation).

Having a min dropout value of 125mV will lead to an increased voltage
for PMIC supplies.

Only set minimum dropout value for ldo enabled mode.

Signed-off-by: Irina Tirdea <irina.tirdea@nxp.com>
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
---
 drivers/regulator/anatop-regulator.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Comments

Mark Brown March 24, 2017, 12:54 p.m. UTC | #1
On Wed, Mar 22, 2017 at 06:53:07PM +0200, Leonard Crestez wrote:

> +	if (anatop_reg->bypass)
> +		anatop_reg->rdesc.min_dropout_uV = 0;
> +	else
> +		anatop_reg->rdesc.min_dropout_uV = LDO_MIN_DROPOUT_UV;

No, this is completely broken - you can't expect to randomly change hthe
regulator description at runtime behind the back of the framework and
expect things to work.  If there is a need to do this we need an
interface for getting the current value and a way to notify of changes.

That said I would not expect the dropout voltage to be considered at
all when the regulator is bypassed, since the regulator is not
regulating it doesn't need any headroom.
Leonard Crestez March 28, 2017, 11:52 a.m. UTC | #2
On Fri, 2017-03-24 at 12:54 +0000, Mark Brown wrote:
> On Wed, Mar 22, 2017 at 06:53:07PM +0200, Leonard Crestez wrote:
> > +	if (anatop_reg->bypass)
> > +		anatop_reg->rdesc.min_dropout_uV = 0;
> > +	else
> > +		anatop_reg->rdesc.min_dropout_uV = LDO_MIN_DROPOUT_UV;
> No, this is completely broken - you can't expect to randomly change hthe
> regulator description at runtime behind the back of the framework and
> expect things to work.  If there is a need to do this we need an
> interface for getting the current value and a way to notify of changes.
> 
> That said I would not expect the dropout voltage to be considered at
> all when the regulator is bypassed, since the regulator is not
> regulating it doesn't need any headroom.

It's a more complex solution but this could be handled in the core instead.
Basically the core would treat min_dropout_uV as zero if the regulator is
currently in bypass mode.

In theory a function could be added in regulator_ops to ask a regulator driver
what requirements it has for its supply but this does not seem necessary.

Patch
diff mbox

diff --git a/drivers/regulator/anatop-regulator.c b/drivers/regulator/anatop-regulator.c
index b041f27..64554e8 100644
--- a/drivers/regulator/anatop-regulator.c
+++ b/drivers/regulator/anatop-regulator.c
@@ -38,6 +38,8 @@ 
 #define LDO_POWER_GATE			0x00
 #define LDO_FET_FULL_ON			0x1f
 
+#define LDO_MIN_DROPOUT_UV		125000
+
 struct anatop_regulator {
 	const char *name;
 	u32 control_reg;
@@ -153,6 +155,10 @@  static int anatop_regmap_set_bypass(struct regulator_dev *reg, bool enable)
 
 	sel = enable ? LDO_FET_FULL_ON : anatop_reg->sel;
 	anatop_reg->bypass = enable;
+	if (anatop_reg->bypass)
+		anatop_reg->rdesc.min_dropout_uV = 0;
+	else
+		anatop_reg->rdesc.min_dropout_uV = LDO_MIN_DROPOUT_UV;
 
 	return regulator_set_voltage_sel_regmap(reg, sel);
 }
@@ -264,7 +270,7 @@  static int anatop_regulator_probe(struct platform_device *pdev)
 	rdesc->vsel_reg = sreg->control_reg;
 	rdesc->vsel_mask = ((1 << sreg->vol_bit_width) - 1) <<
 			   sreg->vol_bit_shift;
-	rdesc->min_dropout_uV = 125000;
+	rdesc->min_dropout_uV = LDO_MIN_DROPOUT_UV;
 
 	config.dev = &pdev->dev;
 	config.init_data = initdata;
@@ -286,6 +292,7 @@  static int anatop_regulator_probe(struct platform_device *pdev)
 		if (sreg->sel == LDO_FET_FULL_ON) {
 			sreg->sel = 0;
 			sreg->bypass = true;
+			rdesc->min_dropout_uV = 0;
 		}
 
 		/*