Re: [PATCH] USB: ehci-hub: wait for RESUME finished when hub try to clear SUSPEND
From: Xiao Jin
Date: Sun May 04 2014 - 10:26:32 EST
On 05/03/2014 11:20 PM, Alan Stern wrote:
On Sat, 3 May 2014, xiao jin wrote:
We use usb ehci to connect with modem and run stress test on ehci
remote wake. Sometimes usb disconnect. We add more debug ftrace
(Kernel version: 3.10) and list the key log to show how problem
happened.
<idle>-0 [000] d.h2 26879.385095: ehci_irq: irq status 1008c PPCE FLR PCD
<idle>-0 [000] d.h2 26879.385099: ehci_irq: rh_state[2] hcd->state[132] pstatus[0][238014c5] suspended_ports[1] reset_done[0]
=> kernel receive a remote wakeup irq from controller
<...>-12873 [000] d..1 26879.393536: ehci_hub_control: GetStatus port:1 status 238014c5 17 ERR POWER sig=k SUSPEND RESUME PE CONNECT
=> PORTSC = 238014c5 (line status = K-state, suspend = 1, force port
resume = 1, J-to-K transition is detected)
<...>-12873 [000] d..1 26879.393549: ehci_hub_control: typeReq [2301] wIndex[1] wValue[2]
<...>-12873 [000] d..1 26879.393553: ehci_hub_control: [ehci_hub_control]line[891] port[0] hostpc_reg [44000202]->[44000202]
<idle>-0 [001] ..s. 26879.403122: ehci_hub_status_data: wgq[ehci_hub_status_data] ignore_oc[0] resuming_ports[1]
<...>-12873 [000] d..1 26879.413379: ehci_hub_control: [ehci_hub_control]line[907] port[0] write portsc_reg[238014c5] reset_done[2105769]
=> kernel write 238014c5 to PORTSC
<...>-12873 [000] d..1 26879.453173: ehci_hub_control: GetStatus port:1 status 23801885 17 ERR POWER sig=j SUSPEND PE CONNECT
=> PORTSC = 23801885 (line status = J-state, suspend = 1), is the status
weird?
<...>-12873 [000] .... 26879.473158: check_port_resume_type: port 1 status 0000.0507 after resume, -19
<...>-12873 [000] .... 26879.473160: usb_port_resume: status = -19 after check_port_resume_type
<...>-12873 [000] .... 26879.473161: usb_port_resume: can't resume, status -19
<...>-12873 [000] .... 26879.473162: hub_port_logical_disconnect: logical disconnect on port 1
This is a little difficult to understand...
We add some debug log manually, please let me explain a little more. See
above "=>".
There is a in-band remote wakeup and controller run in k-state. Then kernel
What do you mean by "in-band"?
We use EHCI as host and have two kinds of mechanism to remote wakeup
event, "in-band" is ehci controller self wakeup, sorry to make you
misunderstanding.
driver(ClearPortFeature/USB_PORT_FEAT_SUSPEND) write RESUME|LS(k-state) bit
into controller.
Why did it do that? Did the kernel try to resume the port at the same
time as the device issued a remote wakeup request? In other words, was
there a race between resume and remote wakeup?
Yes, I mean a race between kernel driver resume and controller remote
wakeup.
It makes controller status weird.
Why? Your log shows that the RESUME bit was already turned on, so
writing a 1 to it shouldn't make any difference. (And the LS(k-state)
bit is RO, so writing a 1 to it shouldn't matter.)
Here the problem is, after remote wakeup, the controller still is in
SUSPEND and kernel report disconnect finally. Could kernel write
"SUSPEND" or "Force Port Resume" bit be related to the problem we meet with?
It's defined in EHCI
controller spec(Revision 1.0), "If it has enabled remote wake-up, a K-state
on the bus will turn the transceiver clock and generate an interrupt. The
software will then have to wait 20 ms for the resume to complete and the
port to go back to an active state."
Where in the spec did you find that quote? It's not present in my copy
of the EHCI Rev 1.0 spec.
I am sorry to make a mistake, I quote it from controller reference
manual. I can find the similar definition in EHCI Rev 1.0,
4.3.1 Port Suspend/Resume.
"When Force Port Resume bit is a one, the host controller sends resume
signaling down the port. System software times the duration of the
resume (nominally 20 milliseconds) then sets the Force Port Resume bit
to a zero."
In this case Kernel should wait for
the wakeup finished, then judge what should do next step.
We have some thought and give a patch. This patch is to wait for controller
RESUME finished when hub try to clear port SUSPEND feature.
This is definitely wrong. For one thing, you mustn't have a 20-ms
delay with interrupts disabled. For another, the spec states (Table
2-16, the entry for bits 11:10) that the Line Status value is valid
only when the port enable bit is 0, so you shouldn't rely on it.
Lastly, there really is no need to do anything, because the remote
wakeup will finish all by itself.
I agree disable irq for maximum 20-ms is not good, but I can find
another case when ehci_hub_control() deal with GetPortStatus.
I have no idea how controller run, from both EHCI spec and reference
manual, I can only deduce that it's better kernel driver don't touch
PORTSC until resume finished. Otherwise how to explain the problem we
meet with? (After remote wakeup, the controller still is in SUSPEND and
kernel report disconnect finally.)
When we try the original change in the mail, we never see the same
problem until now.
Try the patch below instead.
OK.
Jin
Alan Stern
Index: usb-3.15/drivers/usb/host/ehci-hub.c
===================================================================
--- usb-3.15.orig/drivers/usb/host/ehci-hub.c
+++ usb-3.15/drivers/usb/host/ehci-hub.c
@@ -935,7 +935,8 @@ static int ehci_hub_control (
break;
}
#endif
- if (!(temp & PORT_SUSPEND))
+ /* Port not suspended, or remote wakeup in progress? */
+ if (!(temp & PORT_SUSPEND) || (temp & PORT_RESUME))
break;
if ((temp & PORT_PE) == 0)
goto error;
--
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