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

[Hans de Goede]

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 ?

The biggest change here is the change in timing ...

Also try defining debug printf in usb_hub.c and see what
output you get ?

Regards,

Hans