linux-kernel - Re: [PATCH] usb: musb: fix MUSB_QUIRK_B_DISCONNECT

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Date:   Mon, 31 May 2021 14:40:34 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Bin Liu <b-liu@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] usb: musb: fix MUSB_QUIRK_B_DISCONNECT_99 handling

* Alexandre Belloni <alexandre.belloni@...tlin.com> [210528 15:35]:
> On 28/05/2021 16:04:46+0200, Thomas Petazzoni wrote:
> > In commit 92af4fc6ec33 ("usb: musb: Fix suspend with devices
> > connected for a64"), the logic to support the
> > MUSB_QUIRK_B_DISCONNECT_99 quirk was modified to only conditionally
> > schedule the musb->irq_work delayed work.
> > 
> > This commit badly breaks ECM Gadget on AM335X. Indeed, with this
> > commit, one can observe massive packet loss:
> > 
> > $ ping 192.168.0.100
> > ...
> > 15 packets transmitted, 3 received, 80% packet loss, time 14316ms
> > 
> > Reverting this commit brings back a properly functioning ECM
> > Gadget. An analysis of the commit seems to indicate that a mistake was
> > made: the previous code was not falling through into the
> > MUSB_QUIRK_B_INVALID_VBUS_91, but now it is, unless the condition is
> > taken.
> > 
> > Changing the logic to be as it was before the problematic commit *and*
> > only conditionally scheduling musb->irq_work resolves the regression:
> > 
> > $ ping 192.168.0.100
> > ...
> > 64 packets transmitted, 64 received, 0% packet loss, time 64475ms
> > 
> > Fixes: 92af4fc6ec33 ("usb: musb: Fix suspend with devices connected for a64")
> > Signed-off-by: Thomas Petazzoni <thomas.petazzoni@...tlin.com>
> Tested-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

Ouch, sorry about that one. And thanks for fixing it:

Acked-by: Tony Lindgren <tony@...mide.com>