[U-Boot] The purpose of enabling CONFIG_PCI_BOOTDELAY

[Andrew Dyer]

On Wed, Mar 24, 2010 at 4:10 PM, Wolfgang Denk <wd at denx.de> wrote:
> Dear Mike,
>
> In message <OF532F17EB.D2119CC3-ON852576F0.0072502F-852576F0.00725A73 at apcc.com> you wrote:
>>
>> What is the purpose of CONFIG_PCI_BOOTDELAY? I am using uboot version
>
> Adding a delay so the PCI controllers can come up and stabilize.
>
>> Specifically in my case, all the resets on my board have occurred well
>> before (500 msec) this portion of the code would execute, so it would seem
>> safe to say that any peripherals like PCI controllers would be satisfied
>> reset-wise.
>
> 500ms is not safe. We have seen cases (for example on 440SP / 440SPe)
> where 5...10 seconds (!) were needed.

I've seen this as well, so I agree that 500ms seems reasonable for a
general value.  Per the PCI 2.3 spec, the time is supposed to be min.
100mS.

this pdf is where they added it to PCI 2.2 as an ECN:
http://www.pcisig.com/specifications/conventional/conventional_pci/reset_ecn1_011300.pdf