[RFC] regulator: anatop-regulator: Also provide a delay when voltage decreases

[RFC] regulator: anatop-regulator: Also provide a delay when voltage decreases

[Fabio Estevam]

From: Fabio Estevam <fabio.estevam@freescale.com>

Currently we only wait for a delay for the LDO voltages to settle when it goes
from a lower voltage to a higher one.

Also provide the delay when the opposite transition happens.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
---
Hi Anson/Shawn,

I could not find in the reference manual anywhere that says that the delay
should de done only when the voltage increases.


 drivers/regulator/anatop-regulator.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/anatop-regulator.c b/drivers/regulator/anatop-regulator.c
index 7d7c05e..843c5d1 100644
--- a/drivers/regulator/anatop-regulator.c
+++ b/drivers/regulator/anatop-regulator.c
@@ -70,7 +70,7 @@ static int anatop_regmap_set_voltage_time_sel(struct regulator_dev *reg,
 	int ret = 0;
 
 	/* check whether need to care about LDO ramp up speed */
-	if (anatop_reg->delay_bit_width && new_sel > old_sel) {
+	if (anatop_reg->delay_bit_width) {
 		/*
 		 * the delay for LDO ramp up time is
 		 * based on the register setting, we need
@@ -80,7 +80,7 @@ static int anatop_regmap_set_voltage_time_sel(struct regulator_dev *reg,
 		regmap_read(anatop_reg->anatop, anatop_reg->delay_reg, &val);
 		val = (val >> anatop_reg->delay_bit_shift) &
 			((1 << anatop_reg->delay_bit_width) - 1);
-		ret = (new_sel - old_sel) * (LDO_RAMP_UP_UNIT_IN_CYCLES <<
+		ret = abs(new_sel - old_sel) * (LDO_RAMP_UP_UNIT_IN_CYCLES <<
 			val) / LDO_RAMP_UP_FREQ_IN_MHZ + 1;
 	}
 
-- 
1.8.1.2

Re: [RFC] regulator: anatop-regulator: Also provide a delay when voltage decreases

[Mark Brown]

On Fri, Dec 20, 2013 at 12:48:22PM -0200, Fabio Estevam wrote:

> I could not find in the reference manual anywhere that says that the delay
> should de done only when the voltage increases.

The reason this is normally not done is that generally consumers don't
care too much if the supply is too high but will fail if they get an
undervoltage supply so there's not such a great need to wait.

It can also be hard to tell how quickly the voltage will fall.