[U-Boot] [PATCH v5 4/4] usb: Change power-on / scanning timeout handling

[Marek Vasut]

On 04/02/2016 11:21 PM, Hans de Goede wrote:
> Hi,

Hi!

> On 04/02/2016 12:22 AM, Marek Vasut wrote:
>> On 03/15/2016 01:59 PM, Stefan Roese wrote:
>>> This patch changes the USB port scanning procedure and timeout
>>> handling in the following ways:
>>>
>>> a)
>>> The power-on delay in usb_hub_power_on() is now reduced to a value of
>>> max(100ms, "hub->desc.bPwrOn2PwrGood * 2"). The code does not wait
>>> using mdelay, instead usb_hub_power_on() will wait before querying
>>> the device in the scanning loop later. The total timeout for this
>>> hub, which is 1 second + "hub->desc.bPwrOn2PwrGood * 2" is calculated
>>> and will be used in the following per-port scanning loop as the timeout
>>> to detect active USB devices on this hub.
>>>
>>> b)
>>> Don't delay the minimum delay (for power to stabilize) in
>>> usb_hub_power_on(). Instead skip querying these devices in the scannig
>>> loop until the delay time is reached.
>>>
>>> c)
>>> The ports are now scanned in a quasi parallel way. The current code did
>>> wait for each (unconnected) port to reach its timeout and only then
>>> continue with the next port. This patch now changes this to scan all
>>> ports of all USB hubs quasi simultaneously. For this, all ports are
>>> added
>>> to a scanning list. This list is scanned until all ports are ready
>>> by either a) reaching the connection timeout (calculated earlier), or
>>> by b) detecting a USB device. This results in a faster USB scan time as
>>> the recursive scanning of USB hubs connected to the hub that's currently
>>> being scanned will start earlier.
>>>
>>> One small functional change to the original code is, that ports with
>>> overcurrent detection will now get rescanned multiple times
>>> (PORT_OVERCURRENT_MAX_SCAN_COUNT).
>>>
>>> Without this patch:
>>> starting USB...
>>> USB0:   USB EHCI 1.00
>>> scanning bus 0 for devices... 9 USB Device(s) found
>>>
>>> time: 20.163 seconds
>>>
>>> With this patch:
>>> starting USB...
>>> USB0:   USB EHCI 1.00
>>> scanning bus 0 for devices... 9 USB Device(s) found
>>>
>>> time: 1.822 seconds
>>>
>>> So ~18.3 seconds of USB scanning time reduction.
>>>
>>> Signed-off-by: Stefan Roese <sr at denx.de>
>>> Acked-by: Hans de Goede <hdegoede at redhat.com>
>>> Tested-by: Stephen Warren <swarren at nvidia.com>
>>
>> This breaks DWC2 on SoCkit, I can no longer detect any USB device.
>> USB works without this patch though. Ideas?
> 
> Have you tried simply adding a large sleep before the
> initial uart, or doing an "usb reset" after the initial
> scan ?

Yeah, that doesn't help. But I also sent a few fixes for the DWC2
controller, so let's see. I also finally got Stefan a working board,
so he can start poking around :)

> The biggest change here is the change in timing ...
> 
> Also try defining debug printf in usb_hub.c and see what
> output you get ?

I'll be offloading this to Stefan :)

> Regards,
> 
> Hans


-- 
Best regards,
Marek Vasut