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List:       linux-usb
Subject:    Re: [PATCH v2 1/1] usb: chipidea: udc: workaround for endpoint conflict issue
From:       Fabio Estevam <festevam () gmail ! com>
Date:       2019-05-30 14:11:42
Message-ID: CAOMZO5Ci9KfZBeSp-ukNgOVwjxGYrz4-uftgBZsix_6Ybuw9Eg () mail ! gmail ! com
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Hi Peter,

On Thu, May 30, 2019 at 5:50 AM Peter Chen <peter.chen@nxp.com> wrote:
>
> An endpoint conflict occurs when the USB is working in device mode
> during an isochronous communication. When the endpointA IN direction
> is an isochronous IN endpoint, and the host sends an IN token to
> endpointA on another device, then the OUT transaction may be missed
> regardless the OUT endpoint number. Generally, this occurs when the
> device is connected to the host through a hub and other devices are
> connected to the same hub.
>
> The affected OUT endpoint can be either control, bulk, isochronous, or
> an interrupt endpoint. After the OUT endpoint is primed, if an IN token
> to the same endpoint number on another device is received, then the OUT
> endpoint may be unprimed (cannot be detected by software), which causes
> this endpoint to no longer respond to the host OUT token, and thus, no
> corresponding interrupt occurs.
>
> There is no good workaround for this issue, the only thing the software
> could do is numbering isochronous IN from the highest endpoint since we
> have observed most of device number endpoint from the lowest.
>
> Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
> Cc: Jun Li <jun.li@nxp.com>
> Signed-off-by: Peter Chen <peter.chen@nxp.com>

Should this patch have Cc stable so that it gets applied for older kernels?

> diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
> index 829e947cabf5..21c1344bfc42 100644
> --- a/drivers/usb/chipidea/udc.c
> +++ b/drivers/usb/chipidea/udc.c
> @@ -1622,6 +1622,28 @@ static int ci_udc_pullup(struct usb_gadget *_gadget, int is_on)
>  static int ci_udc_start(struct usb_gadget *gadget,
>                          struct usb_gadget_driver *driver);
>  static int ci_udc_stop(struct usb_gadget *gadget);
> +
> +

One blank line is enough.
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