On Wed, Feb 01, 2017 at 12:10:17AM +0100, Rafael J. Wysocki wrote:

On Tue, Jan 3, 2017 at 7:33 AM, Peter Chen [off-list ref] wrote:

quoted

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
library to cover this requirement. The core code has supplied
some common helpers for host driver, and individual power sequence
libraries handle kinds of power sequence for devices. The pwrseq
librares always need to allocate extra instance for compatible
string match.

pwrseq_generic is intended for general purpose of power sequence, which
handles gpios and clocks currently, and can cover other controls in
future. The host driver just needs to call of_pwrseq_on/of_pwrseq_off
if only one power sequence is needed, else call of_pwrseq_on_list
/of_pwrseq_off_list instead (eg, USB hub driver).

For new power sequence library, it can add its compatible string
to pwrseq_of_match_table, then the pwrseq core will match it with
DT's, and choose this library at runtime.

Signed-off-by: Peter Chen <redacted>
Tested-by: Maciej S. Szmigiero <redacted>
Tested-by Joshua Clayton [off-list ref]
Reviewed-by: Matthias Kaehlcke <redacted>
Tested-by: Matthias Kaehlcke <redacted>

Quite honestly, I have a really hard time with trying to follow this
code and the total lack of documentation makes it even harder.  In
particular, the generic power sequence code is not even commented at
all, so it really is hard to say how this is going to work, let alone
deciding whether or not to apply it.

Plus, of course, the USB core changes must be acked by the maintainer
thereof for me to be able to handle the series.

Ah crap, I wanted you to explain it as I too couldn't figure it out :)

But at this point I basically need you to explain the design to me, please.

Same here.

thanks,

greg k-h
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