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

[Wolfgang Grandegger <wg@grandegger.com>]

On 12/19/2011 05:59 PM, Remy Bohmer wrote:
> Hi Wolfgang,
> 
> 2011/12/19 Wolfgang Grandegger <wg@grandegger.com>:
>> On 12/19/2011 01:51 PM, Vincent Palatin wrote:
>>> On Mon, Dec 19, 2011 at 04:07, Wolfgang Grandegger <wg@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?

OK, should find time tomorrow.

Wolfgang.