From eb51c6eb9775d5e7ef810327dbc84bb0d15f72b5 Mon Sep 17 00:00:00 2001 From: Olliver Schinagl Date: Tue, 11 Dec 2018 17:17:09 +0200 Subject: dt-bindings: mfd: axp20x: Add software based soft_start for AXP209 LDO3 In the past, there have been words on various lists that if LDO3 is disabled in u-boot, but enabled in the DTS, the axp209 driver would fail to continue/hang. Several enable/disable patches have been issues to devicetree's in both the kernel and u-boot to address this issue. What really happened however, was that the AXP209 shuts down without a notice and without setting an interrupt. This is caused when LDO3 gets overloaded, for example with large capacitors on the LDO3 output. Normally, we would expect that AXP209 would source 200 mA as per datasheet and set and trigger an interrupt when being overloaded. For some reason however, this does not happen. As a work-around, implement software-based 'regulator-soft-start' property for AXP209 LDO3 regulator, which is used to first bring up the LDO3 to the lowest possible voltage and then enable the LDO. After that, we can set the requested voltage as usual. Combining this setting with the regulator-ramp-delay allows LDO3 to come up slowly and staggered, potentially reducing overall inrush current. Signed-off-by: Olliver Schinagl Signed-off-by: Priit Laes Signed-off-by: Mark Brown --- Documentation/devicetree/bindings/mfd/axp20x.txt | 3 +++ 1 file changed, 3 insertions(+) diff --git a/Documentation/devicetree/bindings/mfd/axp20x.txt b/Documentation/devicetree/bindings/mfd/axp20x.txt index c6266052d23f..2af4ff95d6bc 100644 --- a/Documentation/devicetree/bindings/mfd/axp20x.txt +++ b/Documentation/devicetree/bindings/mfd/axp20x.txt @@ -37,6 +37,9 @@ more information: - regulator-ramp-delay: sets the ramp up delay in uV/us AXP20x/DCDC2: 1600, 800 AXP20x/LDO3: 1600, 800 +- regulator-soft-start: enable the output at the lowest possible voltage and + only then set the desired voltage + AXP20x/LDO3: software-based implementation Optional properties: - x-powers,dcdc-freq: defines the work frequency of DC-DC in KHz -- cgit v1.2.3