From: Roger Quadros <rogerq@ti.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: <balbi@ti.com>, <tony@atomide.com>, <ruslan.bilovol@ti.com>,
<linux-usb@vger.kernel.org>, <linux-omap@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH 4/6] USB: ehci-omap: Suspend the controller during bus suspend
Date: Mon, 1 Jul 2013 11:16:45 +0300 [thread overview]
Message-ID: <51D13AED.4010307@ti.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1306281346430.1047-100000@iolanthe.rowland.org>
On 06/28/2013 10:06 PM, Alan Stern wrote:
> On Fri, 28 Jun 2013, Roger Quadros wrote:
>
>>> That's not what I meant. Never mind the pinctrl; I was asking about
>>> the EHCI controller itself. Under what circumstances does the
>>> controller assert its wakeup signal? And how do you tell it to stop
>>> asserting that signal?
>>
>> I believe this would be through the EHCI Interrupt enable register (USBINTR).
>> I'm not aware of any other mechanism.
>
> That's strange, because ehci_suspend() sets the intr_enable register to
> 0. So how do you ever get any wakeup interrupts at all?
Because after ehci_suspend() for OMAP, we solely rely on the out of band wake up
mechanism. i.e. Pad wakeup.
>
>> Right. It seems the external hub has signaled remote wakeup but the kernel doesn't
>> resume the root hub's port it is connected to.
>>
>> By observing the detailed logs below you can see that the root hub does not generate
>> an INTerrupt transaction to notify the port status change event. I've captured the pstatus
>> and GetPortStatus info as well.
>
> We don't need an interrupt. The driver is supposed to detect the
> remote wakeup sent by the external hub all by itself.
OK. Then it could point to a bug in our stack.
>
>> Failing case
>> ------------
>>
>> [ 16.108032] usb usb1: usb auto-resume
>> [ 16.108062] ehci-omap 48064800.ehci: resume root hub
>> [ 16.108154] hub 1-0:1.0: hub_resume
>> [ 16.108398] ehci_hub_control GetPortStatus, port 1 temp = 0x1000
>> [ 16.108459] ehci_hub_control GetPortStatus, port 2 temp = 0x14c5
>
> Here's where we should detect it. Look at the GetPortStatus case in
> ehci_hub_control(); the PORT_RESUME bit (0x0040) is set in temp, so the
> "Remote Wakeup received?" code should run. In particular, these lines
> should run:
>
> /* resume signaling for 20 msec */
> ehci->reset_done[wIndex] = jiffies
> + msecs_to_jiffies(20);
> usb_hcd_start_port_resume(&hcd->self, wIndex);
> /* check the port again */
> mod_timer(&ehci_to_hcd(ehci)->rh_timer,
> ehci->reset_done[wIndex]);
>
> Therefore 20 ms later, around timestamp 16.128459,
> ehci_hub_status_data() should have been called. At that time, the
> root-hub port should have been fully resumed.
OK. right.
>
>> [ 16.108551] hub 1-0:1.0: port 2: status 0507 change 0000
>> [ 16.108612] ehci_hub_control GetPortStatus, port 3 temp = 0x1000
>> [ 16.108642] hub 1-0:1.0: hub_activate submitting urb
>> [ 16.109222] ehci_irq port 3 pstatus 0x1000
>> [ 16.109222] ehci_irq port 2 pstatus 0x14c5
>> [ 16.109252] ehci_irq port 1 pstatus 0x1000
>> [ 16.109374] hub 1-0:1.0: state 7 ports 3 chg 0000 evt 0000
>
> But apparently nothing happened. Why not? Did the rh_timer get reset?
> Maybe you can find out what went wrong.
>
Sure. I'll investigate.
> (Hmmm, we seem to be missing a
>
> set_bit(wIndex, &ehci->resuming_ports);
>
> line in there...)
>
>>> Also, why do you need omap->initialized? Do you think you might get a
>>> wakeup interrupt before the controller has been fully set up? I don't
>>> see how you could, given the pm_runtime_get_sync() call in the probe
>>> routine.
>>>
>>
>> During probe we need to runtime_resume the device before usb_add_hcd() since the
>> controller clocks must be enabled before any registers are accessed.
>> However, we cannot call ehci_resume() before usb_add_hcd(). So to prevent this
>> chicken & egg situation, I've used the omap->initialized flag. It only indicates that
>> the ehci structures are initialized and we can call ehci_resume/suspend().
>
> Ah, yes. Other subsystems, such as PCI, face exactly the same problem.
>
> You probably shouldn't call it "initialized", though, because the same
> issue arises in ehci_hcd_omap_remove() -- the pm_runtime_put_sync()
> there would end up calling ehci_suspend() after usb_remove_hcd().
> "bound" or "started" would be better names.
>
OK. Started seems fine.
cheers,
-roger
next prev parent reply other threads:[~2013-07-01 8:17 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-19 14:05 [RFC PATCH 0/6] Suspend USB Host controller on bus suspend Roger Quadros
2013-06-19 14:05 ` [RFC PATCH 1/6] mfd: omap-usb-host: move initialization to module_init() Roger Quadros
2013-06-20 12:07 ` Felipe Balbi
2013-06-20 12:29 ` Roger Quadros
2013-06-19 14:05 ` [RFC PATCH 2/6] mfd: omap-usb-host: Put pins in IDLE state on suspend Roger Quadros
2013-06-19 17:23 ` Kevin Hilman
2013-06-20 7:21 ` Tony Lindgren
2013-06-20 12:30 ` Roger Quadros
2013-06-19 14:05 ` [RFC PATCH 3/6] USB: ehci: allow controller drivers to override irq & bus_suspend/resume Roger Quadros
2013-06-19 14:05 ` [RFC PATCH 4/6] USB: ehci-omap: Suspend the controller during bus suspend Roger Quadros
2013-06-19 17:39 ` Kevin Hilman
2013-06-20 12:32 ` Roger Quadros
2013-06-20 12:11 ` Felipe Balbi
2013-06-20 12:35 ` Roger Quadros
2013-06-20 17:33 ` Alan Stern
2013-06-24 15:09 ` Roger Quadros
2013-06-24 19:34 ` Alan Stern
2013-06-25 13:59 ` Roger Quadros
2013-06-25 17:38 ` Alan Stern
2013-06-26 13:38 ` Roger Quadros
2013-06-27 15:40 ` Alan Stern
2013-06-28 12:20 ` Roger Quadros
2013-06-28 13:57 ` Roger Quadros
2013-06-28 19:18 ` Alan Stern
2013-07-01 8:33 ` Roger Quadros
2013-06-28 19:06 ` Alan Stern
2013-07-01 8:16 ` Roger Quadros [this message]
2013-07-01 16:24 ` Alan Stern
2013-07-01 16:49 ` Felipe Balbi
2013-07-01 21:01 ` Alan Stern
2013-07-02 8:22 ` Roger Quadros
2013-07-02 17:17 ` Alan Stern
2013-07-03 9:13 ` Roger Quadros
2013-07-03 12:57 ` Felipe Balbi
2013-07-03 13:06 ` Roger Quadros
2013-07-03 13:15 ` Felipe Balbi
2013-07-03 14:30 ` Alan Stern
2013-07-09 13:58 ` Roger Quadros
2013-06-19 14:05 ` [RFC PATCH 5/6] ARM: dts: omap3beagle-xm: Add idle state pins for USB host Roger Quadros
2013-06-19 18:42 ` Kevin Hilman
2013-06-20 11:55 ` Roger Quadros
2013-06-20 12:02 ` Roger Quadros
2013-06-20 13:02 ` Roger Quadros
2013-06-19 14:05 ` [RFC PATCH 6/6] ARM: OMAP3: Enable Hardware Save and Restore for USB Host Roger Quadros
2013-06-19 17:30 ` Sergei Shtylyov
2013-06-20 12:42 ` Roger Quadros
2013-06-19 15:23 ` [RFC PATCH 0/6] Suspend USB Host controller on bus suspend Alan Stern
2013-06-20 12:39 ` Roger Quadros
2013-06-20 17:19 ` Alan Stern
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