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To:     Peter Zijlstra <peterz@infradead.org>
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From:   Mathias Nyman <mathias.nyman@linux.intel.com>
Subject: Re: earlyprintk=xdbc seems broken
Message-ID: <6e2700c4-07dd-76ac-cd8f-d9e5b9b24e74@linux.intel.com>
Date:   Tue, 25 Jan 2022 10:51:00 +0200
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On 24.1.2022 18.46, Peter Zijlstra wrote:
> On Mon, Jan 24, 2022 at 05:39:08PM +0100, Peter Zijlstra wrote:
>> On Mon, Jan 24, 2022 at 04:55:22PM +0200, Mathias Nyman wrote:
>>>  
>>>> [    0.000000] xhci_dbc:early_xdbc_parse_parameter: dbgp_num: 0
>>>> [    4.984106] xhci_dbc:xdbc_start: waiting for connection timed out, DCPORTSC:0xa0
>>>> [    9.946159] xhci_dbc:xdbc_start: waiting for connection timed out, DCPORTSC:0xa0
>>>> [    9.946163] xhci_dbc:early_xdbc_setup_hardware: failed to setup the connection to host
>>>>
>>>> [   12.818364] xhci_hcd 0000:00:0d.0: xHCI Host Controller
>>>> [   12.818373] xhci_hcd 0000:00:0d.0: new USB bus registered, assigned bus number 1
>>>> [   12.820360] xhci_hcd 0000:00:0d.0: xHCI Host Controller
>>>> [   12.820363] xhci_hcd 0000:00:0d.0: new USB bus registered, assigned bus number 2
>>>> [   12.821036] xhci_hcd 0000:00:14.0: xHCI Host Controller
>>>> [   12.821040] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 3
>>>> [   12.823451] xhci_hcd 0000:00:14.0: xHCI Host Controller
>>>> [   12.823453] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 4
>>>> [   17.115089] usb usb4-port4: Cannot enable. Maybe the USB cable is bad?
>>>> [   17.115163] usb usb4-port4: config error
>>>
>>> Ok, I see it now.
>>> Your setup has two xhci controllers, earlypringk=dbc enables dbc on the first xhci
>>> it finds, which would be at 0000:00:0d.0.
>>> Your cable is connected to the second xhci host at 0000:00:14.0
>>>
>>> does using "earlyprintk=xdbc1" work?
>>
>> Very quick testing says it don't work.. but I'll try again later, need
>> to go cook dinner now.
> 
> FYI, I'm thinking early_xdbc_parse_parameter should've now given
> dpgp_num: 1 ?
> 

Yes, it should. 

Looks like there's a parsing issue.
"earlyprintk=xdbc1,keep" fails on our Tigerlake as well.
  
Without the "keep" option it works for me:

[    0.000000] Command line: console=ttyS0,115200n8 buildroot_hostname=tgl04 earlyprintk=xdbc1 dmi_entry_point=0x74374000
[    0.000000] xhci_dbc:early_xdbc_parse_parameter: dbgp_num: 1

-Mathias