linux-kernel - Re: [PATCH 1/2] usb: dwc3: gadget: Fix full speed mode

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Message-ID: <cb0fa277-ce28-d80c-3f5e-7c09597942dd@synopsys.com>
Date:   Wed, 7 Dec 2016 19:06:54 -0800
From:   John Youn <John.Youn@...opsys.com>
To:     Felipe Balbi <balbi@...nel.org>, Roger Quadros <rogerq@...com>,
        John Youn <John.Youn@...opsys.com>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb: dwc3: gadget: Fix full speed mode

On 12/7/2016 4:44 AM, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@...com> writes:
>>>> Roger Quadros <rogerq@...com> writes:
>>>>> DCFG.DEVSPD == 0x3 is not valid and we need to set
>>>>> DCFG.DEVSPD to 0x1 for full speed mode.
>>>>
>>>> seems like it has been made invalid somewhere between 1.73a and
>>>> 2.60a. Can you figure it out from Documentation why and when it was made
>>>> invalid? We might need revision checks here.
>>>>
>>>
>>> I'll try to dig out more.
>>
>> I couldn't figure out more information on this. The changelogs in the TRMs
>> don't capture this change and I don't have access to all TRM versions
>> so I can't say which version it got changed and why.
>>
>> Can we please involve someone from Synopsis to provide this information?
>> Thanks.
> 
> John, could you help us with this query? We'd like to understand why one
> of the FULLSPEED modes got removed. Do we need a revision check or can
> we assume that the other mode was never supposed to be used?
> 

Full speed is 0x1. 0x3 may still work due to how the bits are
checked. But it definitely should be 0x1.

I'm not sure if it was 0x3 before. I still need to confirm whether
that was the case or not and if so why.

Regards,
John