linux-kernel - RE: [PATCH v2 3/3] usb: dwc3: gadget: Add support for disabling U1 and U2 entries

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Date:   Fri, 10 May 2019 06:58:09 +0000
From:   Anurag Kumar Vulisha <anuragku@...inx.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Felipe Balbi <balbi@...nel.org>,
        "Claus H. Stovgaard" <cst@...seone.com>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "v.anuragkumar@...il.com" <v.anuragkumar@...il.com>
Subject: RE: [PATCH v2 3/3] usb: dwc3: gadget: Add support for disabling U1
 and U2 entries


Hi Thinh,

>-----Original Message-----
>From: Thinh Nguyen [mailto:Thinh.Nguyen@...opsys.com]
>Sent: Friday, May 10, 2019 5:30 AM
>To: Anurag Kumar Vulisha <anuragku@...inx.com>; Thinh Nguyen
><Thinh.Nguyen@...opsys.com>; Greg Kroah-Hartman
><gregkh@...uxfoundation.org>; Rob Herring <robh+dt@...nel.org>; Mark Rutland
><mark.rutland@....com>; Felipe Balbi <balbi@...nel.org>; Claus H. Stovgaard
><cst@...seone.com>
>Cc: linux-usb@...r.kernel.org; devicetree@...r.kernel.org; linux-
>kernel@...r.kernel.org; v.anuragkumar@...il.com
>Subject: Re: [PATCH v2 3/3] usb: dwc3: gadget: Add support for disabling U1 and U2
>entries
>
>Hi Anurag,
>
>Anurag Kumar Vulisha wrote:
>>>> +		return -EINVAL;
>>>>
>>>>  	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
>>>>  	if (set)
>>>> @@ -626,7 +630,10 @@ static int dwc3_ep0_set_config(struct dwc3 *dwc,
>struct
>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>> index e293400..f2d3112 100644
>>>> --- a/drivers/usb/dwc3/gadget.c
>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>> @@ -2073,6 +2073,24 @@ static int dwc3_gadget_stop(struct usb_gadget *g)
>>>>  	return 0;
>>>>  }
>>>>
>>>> +static void dwc3_gadget_config_params(struct usb_gadget *g,
>>>> +				      struct usb_dcd_config_params *params)
>>>> +{
>>>> +	struct dwc3		*dwc = gadget_to_dwc(g);
>>>> +
>>>> +	/* U1 Device exit Latency */
>>>> +	if (dwc->dis_u1_entry_quirk)
>>>> +		params->bU1devExitLat = 0;
>>> It doesn't make sense to have exit latency of 0. Rejecting
>>> SET_FEATURE(enable U1/U2) should already let the host know that the
>>> device doesn't support U1/U2.
>>>
>> I am okay to remove this, but I feel that it is better to report zero value instead
>> of a non-zero value in exit latency of BOS when U1 or U2 entries are not supported.
>> Advantage of reporting 0 is that some hosts doesn't even send
>SET_FEATURE(U1/U2)
>> requests on seeing zero value in BOS descriptor. Also there can be cases where U1 is
>> disabled and U2 entry is allowed or vice versa, for these kind of cases the driver can
>> set zero exit latency value for U1 and non-zero exit latency value for U2 . Based on
>this
>> I think it would be better to report 0 when U1/U2 states are not enabled. Please
>provide
>> your opinion on this.
>
>Hm... I assume you're testing against linux usb stack and xhci host. If
>that's the case, it looks like host will still request the device to
>enter U1/U2 despite the device rejecting SET_FEATURE(enable U1/U2). This
>needs to be fixed. I think what you have is fine to workaround this issue.

Thanks . Will send the next series with the other fixes that you have suggested

Best Regards,
Anurag Kumar Vulisha