From: Chunfeng Yun <chunfeng.yun@mediatek.com>
To: Roger Quadros <rogerq@ti.com>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>,
Heikki Krogerus <heikki.krogerus@linux.intel.com>,
Pawel Laszczak <pawell@cadence.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"jbergsagel@ti.com" <jbergsagel@ti.com>,
"nsekhar@ti.com" <nsekhar@ti.com>, "nm@ti.com" <nm@ti.com>,
Suresh Punnoose <sureshp@cadence.com>,
Jayshri Dajiram Pawar <jpawar@cadence.com>,
"Rahul Kumar" <kurahul@cadence.com>,
Anil Joy Varughese <aniljoy@cadence.com>
Subject: Re: [PATCH v10 5/6] usb:cdns3 Add Cadence USB3 DRD Driver
Date: Tue, 13 Aug 2019 16:50:28 +0800 [thread overview]
Message-ID: <1565686228.7317.2.camel@mhfsdcap03> (raw)
In-Reply-To: <7c0c5de2-1100-333a-eb0e-52bab4eb9cd5@ti.com>
On Tue, 2019-08-13 at 10:48 +0300, Roger Quadros wrote:
>
> On 13/08/2019 10:30, Chunfeng Yun wrote:
> > On Mon, 2019-08-12 at 16:04 +0300, Roger Quadros wrote:
> >>
> >> On 12/08/2019 15:46, Felipe Balbi wrote:
> >>>
> >>> Hi,
> >>>
> >>> Roger Quadros <rogerq@ti.com> writes:
> >>>>> The sysfs file we expose from the class for the role switches is
> >>>>> primarily meant for supporting proprietary protocols that require us
> >>>>> to basically override the connector USB data role. The default role
> >>>>> should always be selected in the drivers.
> >>>>
> >>>> OK. Let's take this example
> >>>> - Port is dual-role port micro AB.
> >>>> - microAB to type-A adapter is connected which pulls ID low. port transitions
> >>>> to "host" role by the controller driver.
> >>>> - proprietary protocol want to switch role to device role so writes "device" to
> >>>> mode switch sysfs. port transitions to "device" role.
> >>>>
> >>>> Now, how does controller driver know to fall back to HW based role switching?
> >>>
> >>> Use a 'disconnect' or 'suspend' event to go reset it? But that should,
> >>> probably, be done at kernel space, no?
> >>>
> >>
> >> Yes that could be one option.
> >> So after a disconnect, sysfs role should reflect actual hardware role. correct?
> >
> > Maybe it's difficult to support both HW based role switch and SW based
> > role switch by sysfs at the same if the HW's FSM rely on, such as, the
> > state of Vbus pin or ID pin. Likes the upper example, when user writes
> > "device" to mode switch sysfs, the driver should skip the HW state of ID
> > pin, due to it's state is Low, or force it as High.
> >
>
> We do need a clear way of indicating that SW wants to override so HW
> state is ignored.
>
> > Another option way is that introduces a property in DTS to indicate the
> > way the driver want to use (HW based or SW based, usb_role_switch
> > doesn't provide this information for the controller driver), but is not
> > flexible enough.
>
> That is not good enough for us. We need both HW and SW based role switching.
>
> Can we introduce a new state (e.g. "auto") in usb_role_switch. This would
> explicitly indicate the driver to do HW based switching.
But "auto" is not a role?
How about introducing a new attribute in usb_role_switch?
>
> This way we don't need to depend on connect/disconnect events and can
> do role switch tests even without cable/device connected.
>
next prev parent reply other threads:[~2019-08-13 8:50 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-21 18:32 [PATCH v10 0/6] Introduced new Cadence USBSS DRD Driver Pawel Laszczak
2019-07-21 18:32 ` [PATCH v10 1/6] dt-bindings: add binding for USBSS-DRD controller Pawel Laszczak
2019-07-21 18:32 ` [PATCH v10 2/6] usb:common Separated decoding functions from dwc3 driver Pawel Laszczak
2019-07-21 19:05 ` Joe Perches
2019-07-21 20:45 ` Alan Stern
2019-07-21 20:54 ` Joe Perches
2019-07-22 10:06 ` Pawel Laszczak
2019-07-22 11:49 ` gregkh
2019-07-21 18:32 ` [PATCH v10 3/6] usb:common Patch simplify usb_decode_set_clear_feature function Pawel Laszczak
2019-07-21 19:07 ` Joe Perches
2019-07-22 10:12 ` Pawel Laszczak
2019-07-21 18:32 ` [PATCH v10 4/6] usb:common Simplify usb_decode_get_set_descriptor function Pawel Laszczak
2019-07-21 18:32 ` [PATCH v10 5/6] usb:cdns3 Add Cadence USB3 DRD Driver Pawel Laszczak
2019-07-31 3:36 ` Pawel Laszczak
2019-08-07 12:08 ` Roger Quadros
2019-08-11 11:59 ` Pawel Laszczak
2019-08-12 8:45 ` Roger Quadros
2019-08-12 9:43 ` Pawel Laszczak
2019-08-12 10:31 ` Heikki Krogerus
2019-08-12 11:05 ` Roger Quadros
2019-08-12 12:46 ` Felipe Balbi
2019-08-12 13:04 ` Roger Quadros
2019-08-13 5:15 ` Felipe Balbi
2019-08-13 7:30 ` Chunfeng Yun
2019-08-13 7:48 ` Roger Quadros
2019-08-13 8:50 ` Chunfeng Yun [this message]
2019-08-12 10:05 ` Roger Quadros
2019-08-12 11:10 ` Pawel Laszczak
2019-08-14 13:32 ` Roger Quadros
2019-08-15 6:10 ` Felipe Balbi
2019-08-19 8:20 ` Pawel Laszczak
2019-08-14 13:38 ` Roger Quadros
2019-08-14 14:30 ` Pawel Laszczak
2019-08-15 11:22 ` Roger Quadros
2019-08-19 10:30 ` Pawel Laszczak
2019-08-19 10:59 ` Roger Quadros
2019-08-23 8:53 ` Vignesh Raghavendra
2019-08-23 9:39 ` Pawel Laszczak
2019-08-26 2:16 ` Peter Chen
2019-08-26 7:53 ` Pawel Laszczak
2019-07-21 18:32 ` [PATCH v10 6/6] usb:cdns3 Fix for stuck packets in on-chip OUT buffer Pawel Laszczak
2019-07-21 19:03 ` [PATCH v10 0/6] Introduced new Cadence USBSS DRD Driver Pavel Machek
2019-07-22 9:58 ` Pawel Laszczak
2019-07-22 11:48 ` gregkh
2019-07-22 11:56 ` Pavel Machek
2019-07-22 12:11 ` gregkh
2019-07-22 12:11 ` Pawel Laszczak
2019-07-22 21:00 ` Pavel Machek
2019-07-23 4:32 ` Pawel Laszczak
2019-08-07 11:05 ` Roger Quadros
2019-08-08 4:12 ` Pawel Laszczak
2019-08-09 10:36 ` Roger Quadros
2019-08-09 10:44 ` Felipe Balbi
2019-08-13 8:22 ` Pavel Machek
2019-08-15 12:12 ` Roger Quadros
2019-08-15 14:39 ` Alan Stern
2019-08-19 12:08 ` Roger Quadros
2019-08-19 14:19 ` Alan Stern
2019-08-21 9:54 ` Roger Quadros
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1565686228.7317.2.camel@mhfsdcap03 \
--to=chunfeng.yun@mediatek.com \
--cc=aniljoy@cadence.com \
--cc=felipe.balbi@linux.intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=heikki.krogerus@linux.intel.com \
--cc=jbergsagel@ti.com \
--cc=jpawar@cadence.com \
--cc=kurahul@cadence.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=nm@ti.com \
--cc=nsekhar@ti.com \
--cc=pawell@cadence.com \
--cc=rogerq@ti.com \
--cc=sureshp@cadence.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).