Re: [PATCH] usb: musb: fix MUSB_QUIRK_B_DISCONNECT_99 handling

[Drew Fustini]

On Fri, May 28, 2021 at 04:04:46PM +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@xxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>  drivers/usb/musb/musb_core.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
> index 8f09a387b773..4c8f0112481f 100644
> --- a/drivers/usb/musb/musb_core.c
> +++ b/drivers/usb/musb/musb_core.c
> @@ -2009,9 +2009,8 @@ static void musb_pm_runtime_check_session(struct musb *musb)
>  			schedule_delayed_work(&musb->irq_work,
>  					      msecs_to_jiffies(1000));
>  			musb->quirk_retries--;
> -			break;
>  		}
> -		fallthrough;
> +		break;
>  	case MUSB_QUIRK_B_INVALID_VBUS_91:
>  		if (musb->quirk_retries && !musb->flush_irq_work) {
>  			musb_dbg(musb,
> -- 
> 2.31.1

Tested-by: Drew Fustini <drew@xxxxxxxxxxxxxxx>

This patches fixes the problem on the BeagleBone Black (AM3358) where
the USB gadget interfaces would frequently reset. For example:

  configfs-gadget gadget: init rndis
  configfs-gadget gadget: RNDIS RX/TX early activation ...
  usb0: qlen 10
  configfs-gadget gadget: rndis_open
  rndis_set_param_medium: 0 4259840
  usb0: eth_start
  rndis_set_param_dev:
  configfs-gadget gadget: set_config: interface 2 (Mass Storage Function) requested delayed status
  configfs-gadget gadget: delayed_status count 1
  configfs-gadget gadget: reset ncm control 3
  configfs-gadget gadget: init ncm ctrl 3
  configfs-gadget gadget: notify speed 425984000
  configfs-gadget gadget: reset acm ttyGS0
  configfs-gadget gadget: activate acm ttyGS0
  configfs-gadget gadget: acm ttyGS0 serial state 0000
  configfs-gadget gadget: usb_composite_setup_continue
  configfs-gadget gadget: usb_composite_setup_continue: Completing delayed status
  configfs-gadget gadget: rndis req21.00 v0000 i0000 l24
  rndis_msg_parser: RNDIS_MSG_INIT
  configfs-gadget gadget: rndis reqa1.01 v0000 i0000 l1025
  configfs-gadget gadget: rndis req21.00 v0000 i0000 l32
  gen_ndis_query_resp: RNDIS_OID_GEN_PHYSICAL_MEDIUM
  configfs-gadget gadget: rndis reqa1.01 v0000 i0000 l1025
  configfs-gadget gadget: rndis req21.00 v0000 i0000 l76
  gen_ndis_query_resp: RNDIS_OID_802_3_PERMANENT_ADDRESS
  configfs-gadget gadget: rndis reqa1.01 v0000 i0000 l1025
  configfs-gadget gadget: rndis req21.00 v0000 i0000 l32
  gen_ndis_set_resp: RNDIS_OID_GEN_CURRENT_PACKET_FILTER 0000002d
  configfs-gadget gadget: rndis reqa1.01 v0000 i0000 l1025
  configfs-gadget gadget: init ncm
  configfs-gadget gadget: activate ncm
  usb1: qlen 10
  configfs-gadget gadget: ncm_open
  usb1: eth_start
  configfs-gadget gadget: reset ncm
  usb1: gether_disconnect
  configfs-gadget gadget: ncm reqa1.80 v0000 i0003 l28
  configfs-gadget gadget: non-CRC mode selected
  configfs-gadget gadget: ncm req21.8a v0000 i0003 l0
  configfs-gadget gadget: NCM16 selected
  configfs-gadget gadget: ncm req21.84 v0000 i0003 l0
  configfs-gadget gadget: init ncm
  configfs-gadget gadget: activate ncm
  usb1: qlen 10
  configfs-gadget gadget: ncm_open
  usb1: eth_start
  configfs-gadget gadget: acm ttyGS0 req21.20 v0000 i0005 l7
  configfs-gadget gadget: notify speed 425984000
  configfs-gadget gadget: notify connect true

I have posted dmesg log without the patch [1] where this happens often
and the dmesg log with the patch [2] where it does happen at all.

Thank you for fixing this!
Drew

[1] https://gist.github.com/pdp7/bd61e5f78545de182605992254d3eeee
[2] https://gist.github.com/pdp7/95b0f34fa1d423d4764984b400c562cf