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Subject: Re: [PATCH v3 0/2] Tango PCIe controller support
From: Mason <slash.tmp@free.fr>
To: linux-pci <linux-pci@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
Cc: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>,
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On 30/03/2017 22:56, Mason wrote:

> I've run into an issue.
> 
> If I boot the system with earlyprintk enabled (as I've
> been doing throughout my dev), things work as expected.
> 
> But if I boot with earlyprintk disabled, then the system
> does not "see" the PCIe board, because reading the vendor
> ID returns 0xffffffff.
> 
> What we think is happening, is that when earlyprintk is
> disabled, the system proceeds much faster through the
> various inits, and the PCIe init happens when PCIe
> link training has not completed yet.
> 
> If that is the case, then it seems I would need to check
> the link state in my probe function.

I determined empirically that link training takes around
10-15 ms. Though I suppose this might depend on the
specific PCIe board? (I'm only considering x1 link.)

So I added an msleep(20); in the probe function, and in
the config_read callback, I check the link status on the
first read to the device.

Should I msleep(40) to be safe?

Regards.