linux-kernel - Re: [PATCH 1/2] usb: dwc3: core: Introduce dwc3_device

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Date:	Fri, 18 Mar 2016 12:17:38 -0700
From:	John Youn <John.Youn@...opsys.com>
To:	Felipe Balbi <balbi@...nel.org>, Roger Quadros <rogerq@...com>,
	John Youn <John.Youn@...opsys.com>
CC:	<nsekhar@...com>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: dwc3: core: Introduce dwc3_device_reinit()

On 3/16/2016 6:56 AM, Felipe Balbi wrote:
> 
> heh, +john
> 
> Felipe Balbi <balbi@...nel.org> writes:
>> [ text/plain ]
>>
>> Hi,
>>
>> Roger Quadros <rogerq@...com> writes:
>>> [ text/plain ]
>>> We will need this function for a workaround.
>>> The function issues a softreset only to the device
>>> controller and performs minimal re-initialization
>>> so that the device controller can be usable.
>>>
>>> As some code is similar to dwc3_core_init() take out
>>> common code into dwc3_get_gctl_quirks().
>>>
>>> We add a new member (prtcap_mode) to struct dwc3 to
>>> keep track of the current mode in the PRTCAPDIR register.
>>>
>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>
>> I must say, I don't like this at all :-p There's ONE known silicon which
>> needs this because of a poor silicon integration which took an IP with a
>> known erratum where it can't be made to work on lower speeds and STILL
>> was integrated without a superspeed PHY.
>>
>> There's a reason why I never tried to push this upstream myself ;-)
>>
>> I'm really thinking we might be better off adding a quirk flag to skip
>> the metastability workaround and allow this ONE silicon to set the
>> controller to lower speed.
>>
>> John, can you check with your colleagues if we would ever fall into
>> STAR#9000525659 if we set maximum speed to high speed during driver
>> probe and never touch it again ? I would assume we don't really fall
>> into the metastability workaround, right ? We're not doing any sort of
>> PM for dwc3...
>>

Hi Felipe,

I don't know much about this but I will check with the engineers and
get back to you.

John