Until now changing the voltage of a regulator only ever effected the regulator itself, but never its supplies. It's a common pattern though to put LDO regulators behind switching regulators. The switching regulators efficiently drop the input voltage but have a high ripple on their output. The output is then cleaned up by the LDOs. For higher energy efficiency the voltage drop at the LDOs should be minimized. This patch adds support for such a scenario.
A new min_dropout_uv field is added to struct regulator_desc. Regulators can specify the minimun dropout voltage they need for proper function here. Now when the voltage is changed on a regulator the regulator core makes sure that a) before increasing the voltage on the current regulator the supply provides at least the desired voltage plus the minimum dropout b) after decreasing the voltage on the current regulator the supply is optimized to the minimum required voltage within the needs of the consumers of the supply. Calculating the optimum voltage for the supply regulator is a bit tricky since the simple approach of just adding the desired minimum voltage and the minimum dropout is not enough. It may happen that the current regulator does not support the desired minimum voltage, but only a higher one. This means we have to figure out the lowest voltage supported by the regulator that is higher than the minimum desired voltage. The regulator_get_voltage_floor introduced with this series does exactly that. This is a first RFC for this series which probably has some rough edges, but it was already tested successfully on a Phytec PFLA02 i.MX6 board. Please review, any input welcome. Sascha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
