power: add generic power sequence framework

Hi Peter,

Quoted 25 lines · Peter Chen

Hi all,

We have an well-known problem that the device needs to do some power sequence before it can be recognized by related host, the typical example like hard-wired mmc devices and usb devices. This power sequence is hard to be described at device tree and handled by related host driver, so we have created a common power sequence framework to handle this requirement. The generic code is supplied some common helpers from host driver, and individual power sequence driver handles kinds of power sequence for devices.

Since the MMC has already done the similar things, and this power sequence handling can be generic, we use mmc power sequence code as base to create this framework.

This patch set is based on Krzysztof Kozlowski's RFC patch set (v4.7-rc1) [1], and making some changes which can let it be generic. After that, we create a generic power sequence driver for USB devices which handles below things, it includes all input signals for devices I can consider.

- Clock and its frequencies
- GPIO for reset and the duration time
- GPIO for enable
- Regulator for power

Quoted 6 lines

This patch set is tested on i.mx6 sabresx evk using a dts change, I use two hot-plug devices to simulate this use case. The udoo board changes were tested using my last power sequence patch set. [2]

@Maciej S. Szmigiero, Oscar, would you please test them on imx6qdl udoo boards?

Thanks for the patch set, just tested them on my UDOO Quad board and can confirm that USB and on-board hub work fine.

Tested-by Maciej S. Szmigiero <[email protected]>

Maciej