dt-bindings: regulator: twl6030: Add retain-on-reset property

During reset the VMMC regulator doesn't reach 0V and only drops to
1.8V, furthermore the pulse width is under 200us whereas the SD
specification expect 1ms.

For this 2 reasons being able to no reset at all the VMMC during warm
reset and keep the current voltage is a good workaround. The TWL6030
allows this but needs to be aware of it and this configuration should
also be shared with the bootloader.

This is the purpose of this new property: ti,retain-on-reset

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Link: https://lore.kernel.org/r/20190725094542.16547-2-gregory.clement@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/Documentation/devicetree/bindings/regulator/twl-regulator.txt b/Documentation/devicetree/bindings/regulator/twl-regulator.txt
index 74a91c4f8530a4cd17cb5d184554c6cd283163e8..549f80436debca8eed1558f547264967cba89a42 100644 (file)
--- a/Documentation/devicetree/bindings/regulator/twl-regulator.txt
+++ b/Documentation/devicetree/bindings/regulator/twl-regulator.txt
@@ -71,3 +71,10 @@ Example:
                regulator-min-microvolt  = <1000000>;
                regulator-max-microvolt  = <3000000>;
        };
+
+For twl6030 regulators/LDOs:
+
+ - ti,retain-on-reset: Does not turn off the supplies during warm
+                       reset. Could be needed for VMMC, as TWL6030
+                       reset sequence for this signal does not comply
+                       with the SD specification.