linux-kernel - Re: [PATCH] usb: dwc2: gadget: fix ISOC frame overflow handling

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Message-ID: <20181108173654.118f9e3e@donbot>
Date:   Thu, 8 Nov 2018 17:36:53 +0000
From:   John Keeping <john@...anate.com>
To:     Minas Harutyunyan <minas.harutyunyan@...opsys.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "arthur.petrosyan@...opsys.com" <arthur.petrosyan@...opsys.com>
Subject: Re: [PATCH] usb: dwc2: gadget: fix ISOC frame overflow handling

Hi Minas,

On Mon, 5 Nov 2018 08:28:07 +0000
Minas Harutyunyan <minas.harutyunyan@...opsys.com> wrote:

> On 10/23/2018 5:43 PM, John Keeping wrote:
> > By clearing the overrun flag as soon as the target frame is next
> > incremented, we can end up incrementing the target frame more than
> > expected in dwc2_gadget_handle_ep_disabled() when the endpoint's
> > interval is greater than 1.  This happens if the target frame has
> > just wrapped at the point when the endpoint is disabled and the
> > frame number has not yet done so.
> > 
> > Instead, wait until the frame number also wraps and then clear the
> > overrun flag.
> > 
> > Signed-off-by: John Keeping <john@...anate.com>
> > ---
> >   drivers/usb/dwc2/gadget.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> > index 2d6d2c8244de..8da2c052dfa1 100644
> > --- a/drivers/usb/dwc2/gadget.c
> > +++ b/drivers/usb/dwc2/gadget.c
> > @@ -117,7 +117,7 @@ static inline void
> > dwc2_gadget_incr_frame_num(struct dwc2_hsotg_ep *hs_ep) if
> > (hs_ep->target_frame > DSTS_SOFFN_LIMIT) { hs_ep->frame_overrun =
> > true; hs_ep->target_frame &= DSTS_SOFFN_LIMIT;
> > -	} else {
> > +	} else if (hs_ep->parent->frame_number <
> > hs_ep->target_frame) { hs_ep->frame_overrun = false;
> >   	}
> >   }
> >   
> Did you tested mentioned by you scenario? If you see issue can you 
> provide debug log and point the issue line in the log.

It only reproduces very occasionally so it's difficult to capture a full
debug log containing the error.

I applied this patch to capture logging specifically around this
scenario:

-- >8 --
diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index 220c0f9b89b0..3770b9d3b523 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -2722,13 +2722,20 @@ static void dwc2_gadget_handle_ep_disabled(struct dwc2_hsotg_ep *hs_ep)
        }
 
        do {
+               unsigned int target_frame = hs_ep->target_frame;
+               bool frame_overrun = hs_ep->frame_overrun;
+
                hs_req = get_ep_head(hs_ep);
                if (hs_req)
                        dwc2_hsotg_complete_request(hsotg, hs_ep, hs_req,
                                                    -ENODATA);
+
                dwc2_gadget_incr_frame_num(hs_ep);
                /* Update current frame number value. */
                hsotg->frame_number = dwc2_hsotg_read_frameno(hsotg);
+
+               dev_warn(hsotg->dev, "%s: expiring request frame_number=0x%04x target_frame=0x%04x overrun=%u\n",
+                        __func__, hsotg->frame_number, target_frame, frame_overrun);
        } while (dwc2_gadget_target_frame_elapsed(hs_ep));
 
        dwc2_gadget_start_next_request(hs_ep);
-- 8< --

and I captured this log (the first entry is a separate error and then
the remaining ones show this bug being triggered):

[  562.571227] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3eb9 target_frame=0x3ec0
[  562.611213] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff8 target_frame=0x0008
[  562.611219] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff8 target_frame=0x0010
[  562.611223] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0018
[  562.611228] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0020
[  562.611232] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0028
[  562.611236] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0030
[  562.611240] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0038
[  562.611244] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0040
[  562.611249] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0048
[  562.611253] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0050
[  562.611257] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0058
[  562.611261] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0060
[  562.611265] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0068
[  562.611269] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0070
[  562.611274] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0078
[  562.611278] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0080
[  562.611282] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0088
[  562.611286] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0090
[  562.611290] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x0098
[  562.611294] dwc2 ff580000.usb: dwc2_gadget_handle_ep_disabled: expiring request frame_number=0x3ff9 target_frame=0x00a0


This was on v4.19 with an additional patch to disable descriptor DMA
because that seems to be causing problems on RK3288 although I haven't
figured out exactly why it's a problem.


Regards,
John