linux-kernel - Re: [PATCH] usb: dwc3: core: power on PHYs before initializing core

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Message-ID: <871sgtbp2a.fsf@linux.intel.com>
Date:   Fri, 09 Mar 2018 11:01:17 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Roger Quadros <rogerq@...com>,
        Brian Norris <briannorris@...omium.org>
Cc:     William Wu <william.wu@...k-chips.com>, gregkh@...uxfoundation.org,
        heiko@...ech.de, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        frank.wang@...k-chips.com, huangtao@...k-chips.com,
        dianders@...gle.com, briannorris@...gle.com, groeck@...gle.com,
        daniel.meng@...k-chips.com, John.Youn@...opsys.com,
        lin.huang@...k-chips.com
Subject: Re: [PATCH] usb: dwc3: core: power on PHYs before initializing core


Hi,

Roger Quadros <rogerq@...com> writes:
> Hi,
>
> On 08/03/18 18:49, Brian Norris wrote:
>> Hi,
>> 
>> On Thu, Mar 08, 2018 at 12:43:40PM +0200, Felipe Balbi wrote:
>>> William Wu <william.wu@...k-chips.com> writes:
>>>> The dwc3_core_init() gets the PHYs and initializes the PHYs with
>>>> the usb_phy_init() and phy_init() functions before initializing
>>>> core, and power on the PHYs after core initialization is done.
>>>>
>>>> However, some platforms (e.g. Rockchip RK3399 DWC3 with Type-C
>>>> USB3 PHY), it needs to do some special operation while power on
>>>> the Type-C PHY before initializing DWC3 core. It's because that
>>>> the RK3399 Type-C PHY requires to hold the DWC3 controller in
>>>> reset state to keep the PIPE power state in P2 while configuring
>>>> the Type-C PHY, otherwise, it may cause waiting for the PIPE ready
>>>> timeout. In this case, if we power on the PHYs after the DWC3 core
>>>> initialization is done, the core will be reset to uninitialized
>>>> state after power on the PHYs.
>>>>
>>>> Fix this by powering on the PHYs before initializing core. And
>>>> because the GUID register may also be reset in this case, so we
>>>> need to configure the GUID register after powering on the PHYs.
>>>>
>>>> Signed-off-by: William Wu <william.wu@...k-chips.com>
>>>
>>> does this cause any regressions for your boards?
>> 
>> I'm not Roger, but I believe it was determined we don't need this for
>> the Rockchip systems for which William was originally sending this. At
>> least not right now. I believe our PHY init problems were mostly
>> resolved in other ways.
>> 
>> (Although I hear USB is currently pretty broken around suspend/resume
>> for us on -next. Likely unrelated.)
>> 
>> I guess we never clearly replied stating the above. I hope this isn't
>> merged anywhere? Or I guess it's no problem to me at the moment, but it
>> might be needless churn.
>> 
>
> I did some quick tests on TI platforms and didn't see any issues with this patch.
> Since this patch isn't really fixing your problem and we didn't have any
> problems to start with I'd suggest to avoid this churn for now.

fair enough, I won't apply it :-)

-- 
balbi

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