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From: Roger Quadros <rogerq@ti.com>
To: Chunfeng Yun <chunfeng.yun@mediatek.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 10:48:03 +0300
Message-ID: <7c0c5de2-1100-333a-eb0e-52bab4eb9cd5@ti.com> (raw)
In-Reply-To: <1565681434.23705.66.camel@mhfsdcap03>



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.

This way we don't need to depend on connect/disconnect events and can
do role switch tests even without cable/device connected.

-- 
cheers,
-roger
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

  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 [this message]
2019-08-13  8:50                       ` Chunfeng Yun
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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