From: Badhri Jagan Sridharan <badhri@google.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Mats Karrman <mats.dev.list@gmail.com>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Greg KH <gregkh@linuxfoundation.org>,
Felipe Balbi <felipe.balbi@linux.intel.com>,
Oliver Neukum <oneukum@suse.com>,
LKML <linux-kernel@vger.kernel.org>,
USB <linux-usb@vger.kernel.org>
Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class
Date: Tue, 18 Apr 2017 11:52:33 -0700 [thread overview]
Message-ID: <CAPTae5+O83bJm6KL2zWNhYv-SiZ2E490CLt02BbK4hG1xKXraw@mail.gmail.com> (raw)
In-Reply-To: <ce0350a4-f7d9-3fdd-88ee-8cb827ecee2a@roeck-us.net>
Hi Heikki,
I have a question regarding the preferred_role node.
+What: /sys/class/typec/<port>/preferred_role
+Date: March 2017
+Contact: Heikki Krogerus <heikki.krogerus@linux.intel.com>
+Description:
+ The user space can notify the driver about the preferred role.
+ It should be handled as enabling of Try.SRC or Try.SNK, as
+ defined in USB Type-C specification, in the port drivers. By
+ default the preferred role should come from the platform.
+
+ Valid values: source, sink, none (to remove preference)
What is the expected behavior when the userspace changes the
preferred_role node when the port is in connected state ?
1. the state machine re-resolves the port roles right away based on
the new state machine in place ? (or)
2. Wait till the subsequent connect for resolving port roles based on the
new state machine.
For #1 to happen the policy_engine layer would have to reset the port
to resolve the port roles based on the (Try.SRC /Try.SNK/ Default)
new state machine preference.
Say for example when two non-PD devices following none (default state
machine) are connected, the port role resolution is going to be random.
But, if the userspace in one of the devices later changes the
preferred_role to source, then that device is most likely to become source
if the Try.SRC state-machine is re-run.
Does the above question fall under a policy decision ? If so, should there
be another node to say if the port roles have to re-resolved based on the
new state machine right away ?
Thanks !!
On Fri, Mar 10, 2017 at 3:41 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> On 03/10/2017 02:22 PM, Mats Karrman wrote:
>>
>> On 2017-03-08 14:58, Heikki Krogerus wrote:
>>
>>> On Tue, Mar 07, 2017 at 11:30:54PM +0100, Mats Karrman wrote:
>>>>
>>>> If I read Heikki's original suggestion I understand it like the DP
>>>> driver would be
>>>> responsible for AM specific USB PD/VDM communication. But wouldn't that
>>>> lead
>>>> to a lot of code duplication since the AM protocol is the same for all
>>>> drivers of
>>>> a kind?
>>>
>>> No that's not what I mean. I'm still mixing your PD controller with
>>> something else above, sorry about that. Your PD controller driver
>>> should not ideally even need to be aware of Type-C connector, right?
>>> It definitely does not need to do any USB PD communication.
>>
>>
>> Right.
>>
>>> I would imagine you have on top of the DP controller, a mux (which
>>> could be a DP/USB3 PHY like on Rockchip RK3399, discrete mux like
>>> Pericom PI3USB30532, or something else), and a USB Type-C PHY or USB
>>> PD controller. The bus would be tying the mux to the Type-C port (PHY
>>> or PD controller) and its partner (note that it does not tie the mux
>>> to the DP controller). Please correct me if I'm wrong about your
>>> hardware.
>>
>>
>> No, you're correct, a discrete mux and a fusb302.
>>
>>> Assuming that is how your board roughly looks like, the driver for the
>>> mux would be the driver for the DP altmode devices. That driver would
>>> be the one converting things like the Attention messages notifying
>>> about HPD into toggling of GPIOs, or what ever is needed on your
>>> board, etc.
>>
>>
>> OK.
>>
>>> The actual PD communication with VDMs should be considered as just the
>>> protocol, so we probable should have "protocol drivers". For example
>>> DP alternate mode VDMs and communication will always be the same
>>> despite of the hardware. The DP alternate mode "protocol driver" would
>>> then be tied to the alternate mode device for the partner, and that
>>> driver could have its own hooks for what ever is needed, like HPD
>>> signal handling, configuration changes, whatever. In any case,
>>> hopefully making things easy and straightforward for the "mux driver",
>>> _so that it does not need to care about the actual PD communication_.
>>
>>
>> I'm digesting your and Guenter's replies and patches.
>> I will try getting something up and running too soon and hopefully the
>> foggy parts will
>> dissolve. As for now I find it a lot easier to grok Guenter's drivers than
>> to see the
>> advantages and/or disadvantages of an altmode bus :-)
>>
>> @Guenter: There _is_ interest for your fusb302 driver, thank you
>>
>
> Ok, I'll see what I need to do to publish it.
>
> Guenter
>
>
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next prev parent reply other threads:[~2017-04-18 18:52 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-21 14:24 [PATCH v17 0/3] USB Type-C Connector class Heikki Krogerus
2017-02-21 14:24 ` [PATCH v17 1/3] lib/string: add sysfs_match_string helper Heikki Krogerus
2017-02-21 14:24 ` [PATCH v17 2/3] usb: USB Type-C connector class Heikki Krogerus
2017-03-02 15:22 ` Mats Karrman
2017-03-03 3:13 ` Guenter Roeck
2017-03-03 7:29 ` Mats Karrman
2017-03-03 9:48 ` Enric Balletbo Serra
2017-03-03 12:59 ` Heikki Krogerus
2017-03-03 14:49 ` Guenter Roeck
2017-03-03 19:27 ` Mats Karrman
2017-03-06 9:37 ` Oliver Neukum
2017-03-06 13:14 ` Heikki Krogerus
2017-03-07 22:30 ` Mats Karrman
2017-03-08 1:38 ` Guenter Roeck
2017-04-08 23:09 ` USB Type-C Port Manager API concern Mats Karrman
2017-04-09 15:16 ` Guenter Roeck
2017-04-09 21:05 ` Mats Karrman
2017-04-14 2:57 ` Guenter Roeck
2017-04-14 8:30 ` Mats Karrman
2017-03-08 13:58 ` [PATCH v17 2/3] usb: USB Type-C connector class Heikki Krogerus
2017-03-10 22:22 ` Mats Karrman
2017-03-10 23:41 ` Guenter Roeck
2017-04-18 18:52 ` Badhri Jagan Sridharan [this message]
2017-04-19 11:23 ` Heikki Krogerus
2017-04-19 14:45 ` Badhri Jagan Sridharan
2017-04-19 15:14 ` Guenter Roeck
2017-04-19 17:22 ` Badhri Jagan Sridharan
2017-04-19 19:29 ` Guenter Roeck
2017-04-20 12:24 ` Heikki Krogerus
2017-04-20 19:46 ` Badhri Jagan Sridharan
2017-04-21 12:12 ` Heikki Krogerus
2017-04-21 13:14 ` Guenter Roeck
2017-04-21 14:27 ` Rajaram R
2017-04-21 16:43 ` Guenter Roeck
2017-04-22 9:23 ` Rajaram R
2017-04-24 17:50 ` Badhri Jagan Sridharan
2017-04-25 8:26 ` Rajaram R
2017-04-25 14:10 ` Guenter Roeck
2017-04-27 6:20 ` Rajaram R
2017-04-27 18:10 ` Guenter Roeck
2017-04-28 10:52 ` Heikki Krogerus
2017-04-20 11:55 ` Heikki Krogerus
2017-03-03 14:41 ` Guenter Roeck
2017-03-03 3:35 ` Peter Chen
2017-03-03 4:29 ` Guenter Roeck
2017-03-03 4:52 ` Peter Chen
2017-03-03 14:36 ` Guenter Roeck
2017-03-06 1:24 ` Peter Chen
2017-03-03 14:31 ` Heikki Krogerus
2017-03-06 1:15 ` Peter Chen
2017-03-06 13:16 ` Heikki Krogerus
2017-03-07 1:36 ` Peter Chen
2017-03-07 8:57 ` Heikki Krogerus
2017-03-08 1:53 ` Guenter Roeck
2017-03-08 6:50 ` Peter Chen
2017-03-08 14:44 ` Guenter Roeck
2017-03-09 2:00 ` Peter Chen
2017-02-21 14:24 ` [PATCH v17 3/3] usb: typec: add driver for Intel Whiskey Cove PMIC USB Type-C PHY Heikki Krogerus
2017-02-21 15:42 ` [PATCH v17 0/3] USB Type-C Connector class Felipe Balbi
2017-03-21 11:14 ` Heikki Krogerus
2017-03-21 10:23 ` Greg KH
2017-03-21 10:37 ` Heikki Krogerus
2017-03-22 21:15 ` Mats Karrman
2017-03-23 8:16 ` Heikki Krogerus
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