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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
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.
> 



  reply index

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 " 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

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