Hi

-----Original Message-----
From: Baolin Wang [mailto:baolin.wang@linaro.org]
Sent: Thursday, March 31, 2016 1:23 PM
To: Jun Li <redacted>
Cc: Peter Chen <redacted>; Felipe Balbi <balbi@kernel.org>;
Greg KH [off-list ref]; Sebastian Reichel [off-list ref];
Dmitry Eremin-Solenikov [off-list ref]; David Woodhouse
[off-list ref]; Peter Chen [off-list ref]; Alan Stern
[off-list ref]; r.baldyga@samsung.com; Yoshihiro Shimoda
[off-list ref]; Lee Jones [off-list ref]; Mark
Brown [off-list ref]; Charles Keepax
[off-list ref]; patches@opensource.wolfsonmicro.com;
Linux PM list [off-list ref]; USB [off-list ref];
device-mainlining@lists.linuxfoundation.org; LKML <linux-
kernel@vger.kernel.org>
Subject: Re: [PATCH v8 0/4] Introduce usb charger framework to deal with
the usb gadget power negotation

On 30 March 2016 at 18:58, Jun Li [off-list ref] wrote:

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Seems you don't want to guarantee charger type detection is
done before gadget connection(pullup DP), right?
I see you call usb_charger_detect_type() in each gadget usb
state

changes.

I am not sure I get your point correctly, please correct me if
I misunderstand you.
We need to check the charger type at every event comes from the
usb gadget state changes or the extcon device state changes,
which means a new charger plugin or pullup.

According to usb charger spec, my understanding is you can't do
real charger detection procedure *after* gadget
_connection_(pullup DP), also I don't

Why can not? Charger detection is usually from PMIC.

Charger detection process will impact DP/DM line state, see usb
charger spec v1.2 for detail detection process, section 4.6.3 says:

"A PD is allowed to *disconnect* and repeat the charger detection
process multiple times while attached. The PD is required to wait
for a time of at least TCP_VDM_EN max between disconnecting and
restarting the charger detection process."

As Peter mentioned, the charger detection should happen between
VBUS detection and gadget pull up DP for first plug in case. So
when&after gadget connect (pullup DP), you should already know the

charger type.

quoted

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Make sense. In our company's solution, charger detection can be done
by hardware from PMIC at first, then it will not affect the DP/DM
line when gadget starts to enumeration.

I see, charger type detection is done automatically by PMIC when VBUS
is detected in your case, you just assume the process is complete
before SW do gadget connect. To make the framework common, you may do

one time charger type check when vbus is on, and save it to avoid repeat
charger type check.

OK. I'll add one judgement to check if the charger type is set in
'usb_charger_detect_type()' function.

Just adding a judgement isn't enough here, your framework should make sure
usb_charger_detect_type() is called before gadget connect, with that, the
existing caller place just gets the charger type from the saved value.
The real charger type detection done by usb_charger_detect_type() can
be called only when vbus is on.
e.g. maybe in usb_udc_vbus_handler() before usb_udc_connect_control().

--
Baolin.wang
Best Regards

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