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From:   Thinh Nguyen <Thinh.Nguyen@synopsys.com>
To:     Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>,
        "balbi@kernel.org" <balbi@kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
CC:     "v.anuragkumar@gmail.com" <v.anuragkumar@gmail.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/8] usb: dwc3: Correct the logic for checking TRB
 full in __dwc3_prepare_one_trb()
Thread-Topic: [PATCH v2 1/8] usb: dwc3: Correct the logic for checking TRB
 full in __dwc3_prepare_one_trb()
Thread-Index: AQHUNiVe6PVhPxbQeEm3tnXrG8X9Mg==
Date:   Wed, 5 Sep 2018 05:33:39 +0000
Message-ID: <30102591E157244384E984126FC3CB4F544AB897@us01wembx1.internal.synopsys.com>
References: <1534508695-12642-1-git-send-email-anurag.kumar.vulisha@xilinx.com>
 <1534508695-12642-2-git-send-email-anurag.kumar.vulisha@xilinx.com>
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Hi Anurag,=0A=
=0A=
On 8/17/2018 5:25 AM, Anurag Kumar Vulisha wrote:=0A=
> Availability of TRB's are calculated using dwc3_calc_trbs_left(), which=
=0A=
> determines available TRB's based on the HWO bit set in a TRB.=0A=
>=0A=
> __dwc3_prepare_one_trb() is called with a TRB which needs to be prepared=
=0A=
> for transfer. This __dwc3_prepare_one_trb() calls dwc3_calc_trbs_left()=
=0A=
> to determine total available TRBs and set IOC bit if the total available=
=0A=
> TRBs are zero. Since the present working TRB(which is passed as an=0A=
> argument to __dwc3_prepare_one_trb() )  doesn't have HWO bit already set,=
=0A=
> there are chances where dwc3_calc_trbs_left() wrongly calculates this=0A=
> present working TRB as free(since the HWO bit is not yet set). This could=
=0A=
> be a problem. This patch correct this issue by setting HWO bit before=0A=
> calling dwc3_calc_trbs_left()=0A=
>=0A=
> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@xilinx.com>=0A=
> ---=0A=
>  Changes in v2:=0A=
> 	1. Changed the commit message=0A=
> ---=0A=
>  drivers/usb/dwc3/gadget.c | 4 ++--=0A=
>  1 file changed, 2 insertions(+), 2 deletions(-)=0A=
>=0A=
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c=0A=
> index 69bf137..f73d219 100644=0A=
> --- a/drivers/usb/dwc3/gadget.c=0A=
> +++ b/drivers/usb/dwc3/gadget.c=0A=
> @@ -990,6 +990,8 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *de=
p, struct dwc3_trb *trb,=0A=
>  			trb->ctrl |=3D DWC3_TRB_CTRL_ISP_IMI;=0A=
>  	}=0A=
>  =0A=
> +	trb->ctrl |=3D DWC3_TRB_CTRL_HWO;=0A=
> +=0A=
>  	if ((!no_interrupt && !chain) ||=0A=
>  			(dwc3_calc_trbs_left(dep) =3D=3D 0))=0A=
>  		trb->ctrl |=3D DWC3_TRB_CTRL_IOC;=0A=
> @@ -1000,8 +1002,6 @@ static void __dwc3_prepare_one_trb(struct dwc3_ep *=
dep, struct dwc3_trb *trb,=0A=
>  	if (usb_endpoint_xfer_bulk(dep->endpoint.desc) && dep->stream_capable)=
=0A=
>  		trb->ctrl |=3D DWC3_TRB_CTRL_SID_SOFN(stream_id);=0A=
>  =0A=
> -	trb->ctrl |=3D DWC3_TRB_CTRL_HWO;=0A=
> -=0A=
>  	trace_dwc3_prepare_trb(dep, trb);=0A=
>  }=0A=
>  =0A=
How do you reproduce this issue? We should not set HWO before setting=0A=
other trb->ctrl bits. Can you provide a driver tracepoint? If there's an=0A=
issue with the check if ((!no_interrupt && !chain) ||=0A=
dwc3_calc_trbs_left =3D=3D 0), then we may need to fix the check there.=0A=
=0A=
BR,=0A=
Thinh=0A=