linux-kernel - [RFC][PATCH 0/3] add EXTCON_CHG_USB

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Message-Id: <20170414184330.22296-1-damien.riegel@savoirfairelinux.com>
Date:   Fri, 14 Apr 2017 14:43:27 -0400
From:   Damien Riegel <damien.riegel@...oirfairelinux.com>
To:     linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        kernel@...oirfairelinux.com,
        Damien Riegel <damien.riegel@...oirfairelinux.com>
Subject: [RFC][PATCH 0/3] add EXTCON_CHG_USB_* cables to MSM USB phy

This patchset adds a way for the MSM USB phy to notify a power supply
when the charging state changes. It achieves that using the extcon
subsystem.

The first patch makes sure msm_otg_notify_charger is called after the
charger attributes have been set.
The second one makes sure that function is called when unplugging a
"in-the-wall" charger.
The last one adds EXTCON_CHG_USB_* cables to the phy.

I send this patchset as RFC because it seems a bit peculiar to have
different drivers that generate the EXTCON_USB_* and EXTCON_CHG_USB_*
events, so I want to make sure to get things right.

As far as I can tell, all the drivers in the kernel that have USB
charger events also have the EXTCON_USB one. In this case, this patchset
would make things a bit different for the MSM phy:

       +----------+      +--------------+
       |   gpio   |      |     PMIC     |<-+
       +----------+      +--------------+  |
           |                    |          |
           `--------------------+          |  EXTCON_CHG_USB_*
                                |          |       events
                    EXTCON_USB  |          |
                      events    |          |
                               \|/         |
                         +--------------+  |
                         |   USB PHY    |--+
                         +--------------+

Text version: EXTCON_USB comes from a GPIO or a PMIC, that triggers a
notifier in the USB phy. That notifier will determine the new
EXTCON_CHG_USB_XXX state and the PMIC will be notified about it and
determine how much current it can use to charge a battery.

Please let me know if this is the correct way to go.

Damien Riegel (3):
  usb: phy: msm: notify charger after setting charger info
  usb: phy: msm: notify charger when power supply is unplugged
  usb: phy: msm: use extcon to notify charger

 drivers/usb/phy/phy-msm-usb.c | 47 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

-- 
2.12.2