On Wed, Feb 03, 2016 at 01:39:02PM +0800, menghui lin wrote:

On Tue, 2016-02-02 at 19:38 +0000, Mark Brown wrote:

quoted

How does the driver know if it needs to change the mode (ie, how can it
tell if the current mode is inadequate) and surely if we can only change
in one direction this isn't terribly useful?

I think the datasheet of buck/ldo could provide information about power
capability of each mode. The driver should adjust regulator mode per its
device's power requirement.

That's of no help for a consumer driver which doesn't know what
regulator is supplying it.

case 1:

We have a USB typeC micro-controller, which has two modes - standby and
normal. It requires 1.8V and 3.3V to operate (both powers are always
on). The device stays in standby mode when there is no cable in. When
cable in, we got an interrupt and change device into normal mode.

The standby mode power consumption is quite small, so we would like the
change mode of regulator into STANDBY to save more power. And we change
into NORMAL when we receive cable-in interrupt.

This seems like something that we ought to be doing via runtime PM
anyway which should be going through the suspend mode bindings, though
that would need some plumbing in.

case 2:

About buck regulator for CPU, it usually provides PWM mode, PWM/PFM Auto
mode, PFM mode. I think it could map to FAST, NORMAL, IDLE mode
respectively. Most of time we would use just normal mode. However, we
would change regulator into PWM mode time to time to test buck output
performance on the tested board.

That's a test use that doesn't seem a good fit for upstream at all.
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