[PATCH v11 4/8] usb: core: add power sequence handling for USB devices

On Thu, Jan 05, 2017 at 02:01:55PM +0800, Peter Chen wrote:

Some hard-wired USB devices need to do power sequence to let the
device work normally, the typical power sequence like: enable USB
PHY clock, toggle reset pin, etc. But current Linux USB driver
lacks of such code to do it, it may cause some hard-wired USB devices
works abnormal or can't be recognized by controller at all.

In this patch, it calls power sequence library APIs to finish
the power sequence events. It will do power on sequence at hub's
probe for all devices under this hub (includes root hub).
At hub_disconnect, it will do power off sequence which is at powered
on list.

Signed-off-by: Peter Chen <redacted>
Tested-by Joshua Clayton [off-list ref]
Tested-by: Maciej S. Szmigiero <redacted>
Reviewed-by: Vaibhav Hiremath <hvaibhav.linux@gmail.com>
---
 drivers/usb/Kconfig    |  1 +
 drivers/usb/core/hub.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
 drivers/usb/core/hub.h |  1 +
 3 files changed, 46 insertions(+), 4 deletions(-)

Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested on Odroid U3 (reset sequence for LAN9730):
Tested-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof