From: Alan Stern <stern@rowland.harvard.edu>
To: Bin Liu <b-liu@ti.com>
Cc: linux-usb@vger.kernel.org
Subject: Re: [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened
Date: Wed, 13 May 2020 21:32:05 -0400 [thread overview]
Message-ID: <20200514013205.GA10515@rowland.harvard.edu> (raw)
In-Reply-To: <20200513213620.21541-1-b-liu@ti.com>
On Wed, May 13, 2020 at 04:36:20PM -0500, Bin Liu wrote:
> When a USB device attached to a hub got disconnected, MUSB controller
> generates RXCSR_RX_ERROR interrupt for the 3-strikes-out error.
>
> Currently the MUSB host driver returns -EPROTO in current URB, then the
> USB device driver could immediately resubmit the URB which causes MUSB
> generate RXCSR_RX_ERROR interrupt again. This circle causes interrupt
> storm then the hub never got a chance to report the USB device detach.
>
> To fix the interrupt storm, change the URB return code to -ESHUTDOWN for
> MUSB_RXCSR_H_ERROR interrupt, so that the USB device driver will not
> immediately resubmit the URB.
>
> Signed-off-by: Bin Liu <b-liu@ti.com>
Strictly speaking, this is not the right thing to do. It goes against
the API described in error-codes.rst. A better approach would be to fix
the drivers that immediately resubmit an URB after getting a -EPROTO
error. After all, that is the wrong thing to do no matter what sort of
host controller the device is attached to.
Alan Stern
next prev parent reply other threads:[~2020-05-14 1:32 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 21:36 [PATCH] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened Bin Liu
2020-05-14 1:32 ` Alan Stern [this message]
2020-05-14 14:28 ` Bin Liu
2020-05-14 14:40 ` Alan Stern
2020-05-14 15:02 ` Bin Liu
2020-05-14 15:37 ` Bin Liu
2020-05-14 16:26 ` Alan Stern
2020-05-14 17:00 ` Bin Liu
2020-05-14 18:55 ` Alan Stern
2020-05-19 17:12 ` Bin Liu
2020-05-19 20:01 ` Alan Stern
2020-05-20 14:31 ` Bin Liu
2020-05-20 16:40 ` Alan Stern
2020-05-20 18:05 ` Bin Liu
2020-05-20 18:25 ` Alan Stern
2020-05-20 18:59 ` Bin Liu
2020-05-19 17:28 ` [PATCH v2] " Bin Liu
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