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

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Message-ID: <56F03FD7.30202@synopsys.com>
Date:	Mon, 21 Mar 2016 11:39:19 -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" <nsekhar@...com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: dwc3: core: Introduce dwc3_device_reinit()

On 3/18/2016 12:17 PM, John Youn wrote:
> 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,

Do you mean to keep DCFG.speed to SS and set dwc->maximum_speed to HS?
I don't see an issue with that as long as we always ignore
dwc->maximum_speed when programming DCFG.speed for all affected
versions of the core. As long as the DCFG.speed = SS, you should not
hit the STAR.

John