Re: iMX6q PCIe phy link never came up on kernel v4.4.x

[Roberto Fichera <kernel@tekno-soft.it>]

On 03/16/2016 10:33 PM, Tim Harvey wrote:
> On Wed, Mar 16, 2016 at 7:19 AM, Fabio Estevam <festevam@gmail.com> wrote:
>> Tim,
>>
>> On Tue, Mar 15, 2016 at 11:29 AM, Roberto Fichera <kernel@tekno-soft.it> wrote:
>>> On 03/15/2016 03:10 PM, Fabio Estevam wrote:
>>>> On Tue, Mar 15, 2016 at 8:08 AM, Roberto Fichera <kernel@tekno-soft.it> wrote:
>>>>
>>>>> Just to say that I've fixed the problem by asserting PERST before to drop PCIe refclk and enable
>>>>> power down. PERST is finally released at the usual place.
>>>> Excellent! Do you plan to submit a patch to fix this issue?
>>> I don't know, in my case the problem was related to the XIO2001 that require PERST to be
>>> asserted before to drop PCIe refclk as reported by its datasheet:
>> Does your board detect XIO2001 bridge with kernel 4.4.x or do you also
>> need something like Roberto's changes below?
>>
> Fabio,
>
> The board combination I have where an XIO2001 is connected directly to
> an IMX6 is a bit different from Roberto's setup. In our configuration
> the XIO2001 is on an 'expansion' board that its own local PCI clock
> generation. So, in my case the XIO2001 always has a valid clock
> before/during/after its reset. This is different from Roberto's
> scenario. I do recall running into an issue with the XIO2001 on
> another product with a different host controller that had to do with
> noise on the clk prior to its reset being asserted so I am not too
> surprised at what Roberto has found.
>
> I don't specifically see an issue with a change that asserts PCI_RST#
> before the CLK gets enabled then de-asserts it after at least 100ms
> has expired from clock enable - I think that actually follows the
> specs wording closer than what we currently do (turning o the clock
> prior to assert/de-assert reset). However I get very nervous at any
> change to the IMX6 PCIe init. We have found it to be very finicky
> because of the lack of a proper reset.
>
> Roberto,
>
> Did you require the changes regarding Gen2 negotiation? My
> IMX6+XIO2001 links reliably at Gen1 which makes sense for that chip.
You are right, I did all my tests again removing all applied changes related
to Gen2 negotiation, and indeed the links goes up correctly at Gen1.

>
> Regards,
>
> Tim
>