[U-Boot] [PATCH] ehci: speed up initialization

[Remy Bohmer]

Hi Wolfgang,

2011/12/19 Wolfgang Grandegger <wg at grandegger.com>:
> On 12/19/2011 01:51 PM, Vincent Palatin wrote:
>> On Mon, Dec 19, 2011 at 04:07, Wolfgang Grandegger <wg at grandegger.com> wrote:
>>> I just realized that this patch breaks "usb start" on my mx53loco board:
>>>
>>> The device is not found at the first attempt. Obviously, a value of 10
>>> for bPwrOn2PwrGood seems too short but 20 works fine. Would that be a
>>> resonable compromise? If yes, I could send a patch.
>>
>> This doesn't match the EHCI standard which explicity states that the
>> power should be good after 20ms (paragraph 2.3.9 in EHCI 1.0), so we
>> should probably find whether we are missing another delay somewhere in
>> the generic EHCI code (which used to be hidden and should be fixed) or
>> if i.MX53 is not compliant with the standard and need a special quirk.
>
> I'm not an USB expert but if I look into the hub_power_on() function of
> the Linux kernel it waits at least 100ms (and only once). See:
>
>  http://lxr.linux.no/#linux+v3.1.5/drivers/usb/core/hub.c#L567

I would prefer a solution in line with the specification, but what is
the reason why Linux takes 100 msec here?
Is that just chosen randomly , or was there a good reason for it?
If there is a good reason (which I assume) I would prefer to follow
Linux here and go for the 100 msec.

Can you please provide a patch?

Kind regards,

Remy