linux-kernel - Applied "dt-bindings: mfd: axp20x: Add software based soft_start for AXP209 LDO3" to the regulator tree

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Date:   Thu, 13 Dec 2018 18:11:37 +0000 (GMT)
From:   Mark Brown <broonie@...nel.org>
To:     Olliver Schinagl <oliver@...inagl.nl>
Cc:     Priit Laes <plaes@...es.org>, Mark Brown <broonie@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Applied "dt-bindings: mfd: axp20x: Add software based soft_start for AXP209 LDO3" to the regulator tree

The patch

   dt-bindings: mfd: axp20x: Add software based soft_start for AXP209 LDO3

has been applied to the regulator tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From eb51c6eb9775d5e7ef810327dbc84bb0d15f72b5 Mon Sep 17 00:00:00 2001
From: Olliver Schinagl <oliver@...inagl.nl>
Date: Tue, 11 Dec 2018 17:17:09 +0200
Subject: [PATCH] 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 <oliver@...inagl.nl>
Signed-off-by: Priit Laes <plaes@...es.org>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 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
-- 
2.19.0.rc2