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Date: Tue, 19 Dec 2023 20:05:15 +0530
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Subject: Re: [Patch v2 2/2] thunderbolt: Teardown tunnels and reset downstream
 ports created by boot firmware
To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Sanath S <Sanath.S@amd.com>, mario.limonciello@amd.com,
 andreas.noever@gmail.com, michael.jamet@intel.com, YehezkelShB@gmail.com,
 linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
References: <c7d174d3-028f-9ce4-7ef5-3e033c195159@amd.com>
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From: Sanath S <sanaths2@amd.com>
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On 12/19/2023 5:56 PM, Mika Westerberg wrote:
> On Tue, Dec 19, 2023 at 02:41:08PM +0530, Sanath S wrote:
>> On 12/18/2023 6:48 PM, Mika Westerberg wrote:
>>> On Mon, Dec 18, 2023 at 06:35:13PM +0530, Sanath S wrote:
>>>> On 12/18/2023 5:53 PM, Mika Westerberg wrote:
>>>>> On Mon, Dec 18, 2023 at 01:31:51PM +0200, Mika Westerberg wrote:
>>>>>> On Mon, Dec 18, 2023 at 04:49:13PM +0530, Sanath S wrote:
>>>>>>>> The discover part should not do anything (like write the hardware) so
>>>>>>>> perhaps it is just some timing thing (but that's weird too).
>>>>>>>>
>>>>>>>> I think we should do something like this:
>>>>>>>>
>>>>>>>> 1. Disable all enabled protocol adapters (reset them to defaults).
>>>>>>>> 2. Clear all protocol adapter paths.
>>>>>>>> 3. Issue DPR over all enabled USB4 ports.
>>>>>>>>
>>>>>>>> BTW, what you mean "didn't work"?
>>>>>>> Path activation would go fine after DPR like below:
>>>>>>>
>>>>>>> [   15.090905] thunderbolt 0000:c4:00.5: 0:5 <-> 2:9 (PCI): activating
>>>>>>> [   15.090932] thunderbolt 0000:c4:00.5: activating PCIe Down path from 0:5
>>>>>>> to 2:9
>>>>>>> [   15.091602] thunderbolt 0000:c4:00.5: activating PCIe Up path from 2:9 to
>>>>>>> 0:5
>>>>>>>
>>>>>>> But, PCIE enumeration doesn't happen (pcie link up will not happen, will not
>>>>>>> see below logs)
>>>>>>> [   15.134223] pcieport 0000:00:03.1: pciehp: Slot(0-1): Card present
>>>>>>> [   15.134243] pcieport 0000:00:03.1: pciehp: Slot(0-1): Link Up
>>>>>> Okay, what if you like reset the PCIe adapter config spaces back to the
>>>>>> defaults? Just as an experiment.
>>>>> If this turns out to be really complex then I guess it is better to do
>>>>> it like you did originally using discovery but at least it would be nice
>>>>> to see what the end result of this experiment looks like :)
>> I feel it's better to go with discover and then reset for now (as v3).
>> I'll keep this experiment as "to do" and will send out when I crack it down.
> Fair enough.
>
>>>> Yes, I'll give a try.
>>>> As an experiment, I tried to compare the path deactivation that occurs at
>>>> two place.
>>>> 1. In tb_switch_reset where we are calling tb_path_deactivate_hop(port, i).
>>>> 2. While we get a unplug event after doing DPR.
>>>>
>>>> I observed both have different hop_index and port numbers.
>>>> So, are we calling tb_path_deactivate_hop with wrong hop ids ?
>>> Wrong adapters possibly.
>>>
>>>>   From deactivate tunnel (called while unplug) :
>>>> [    3.408268] thunderbolt 0000:c4:00.5: deactivating PCIe Down path from
>>>> 2:9 to 0:5
>>>> [    3.408282] deactivate hop port = 9 hop_index=8
>>>> [    3.408328] deactivate hop port = 2 hop_index=10
>>> Definitely should be port = 5 (that's PCIe down in your log) and
>>> hop_index = 8 (that's the one used with PCIe).
>>>
>>>> Deactivate from tb_switch_reset() :
>>>> deactivate hop port = 5 hop_index=8
>>> Can you add some more logging and provide me the dmesg or
>>> alternativively investigate it yourself. You can use tb_port_dbg() to
>>> get the port numbers to the log.
>> I've sent you complete dmesg.
> Got it, thanks!
>
>> Here is the log w.r.t port numbers and path clean up.
>>
>> [    3.389038] thunderbolt 0000:c4:00.5: 0:3: Downstream port, setting DPR
>> [    3.389065] Calling usb4_port_reset
>> [    3.389068] thunderbolt 0000:c4:00.5: 0:4: Found USB3 DOWN
>> [    3.389193] thunderbolt 0000:c4:00.5: 0:4: In reset, cleaning up path,
>> port->port = 4 hopid = 8
>> [    3.389203] thunderbolt 0000:c4:00.5: 0:4: deactivating_hop port = 4
>> hop_index=8
>> [    3.389682] thunderbolt 0000:c4:00.5: 0:5: Found PCI Down
>> [    3.389811] thunderbolt 0000:c4:00.5: 0:5: In reset, cleaning up path,
>> port->port = 5 hopid = 8
>> [    3.389817] thunderbolt 0000:c4:00.5: 0:5: deactivating_hop port = 5
>> hop_index=8
>> [    3.390296] thunderbolt 0000:c4:00.5: 0:6: Found DP IN
>> [    3.390555] thunderbolt 0000:c4:00.5: 0:6: In reset, cleaning up path,
>> port->port = 6 hopid = 8
>> [    3.390558] thunderbolt 0000:c4:00.5: 0:6: deactivating_hop port = 6
>> hop_index=8
>> [    3.390686] thunderbolt 0000:c4:00.5: 0:6: In reset, cleaning up path,
>> port->port = 6 hopid = 9
>> [    3.390689] thunderbolt 0000:c4:00.5: 0:6: deactivating_hop port = 6
>> hop_index=9
>> [    3.390816] thunderbolt 0000:c4:00.5: 0:7: Found DP IN
>> [    3.391077] thunderbolt 0000:c4:00.5: 0:7: In reset, cleaning up path,
>> port->port = 7 hopid = 8
>> [    3.391080] thunderbolt 0000:c4:00.5: 0:7: deactivating_hop port = 7
>> hop_index=8
>> [    3.391213] thunderbolt 0000:c4:00.5: 0:7: In reset, cleaning up path,
>> port->port = 7 hopid = 9
>> [    3.391217] thunderbolt 0000:c4:00.5: 0:7: deactivating_hop port = 7
>> hop_index=9
>> [    3.391342] Reset success
>> [    3.391391] thunderbolt 0000:c4:00.5: 0:2: switch unplugged
>> [    3.391434] thunderbolt 0000:c4:00.5: 0:4 <-> 2:16 (USB3): deactivating
>> [    3.391471] thunderbolt 0000:c4:00.5: deactivating USB3 Down path from
>> 0:4 to 2:16
>> [    3.391477] thunderbolt 0000:c4:00.5: 0:4: deactivating_hop port = 4
>> hop_index=8
>> [    3.391641] thunderbolt 0000:c4:00.5: 2:1: deactivating_hop port = 1
>> hop_index=9
>> [    3.391651] thunderbolt 0000:c4:00.5: deactivating USB3 Up path from 2:16
>> to 0:4
>> [    3.391659] thunderbolt 0000:c4:00.5: 2:16: deactivating_hop port = 16
>> hop_index=8
>> [    3.391664] thunderbolt 0000:c4:00.5: 0:2: deactivating_hop port = 2
>> hop_index=9
>> [    3.391701] thunderbolt 0000:c4:00.6: total paths: 3
>> [    3.391720] thunderbolt 0000:c4:00.6: IOMMU DMA protection is disabled
>> [    3.392027] thunderbolt 0000:c4:00.5: 0:5 <-> 2:9 (PCI): deactivating
>> [    3.392154] thunderbolt 0000:c4:00.5: deactivating PCIe Down path from
>> 2:9 to 0:5
>> [    3.392163] thunderbolt 0000:c4:00.5: 2:9: deactivating_hop port = 9
>> hop_index=8
>> [    3.392170] thunderbolt 0000:c4:00.5: 0:2: deactivating_hop port = 2
>> hop_index=10
>> [    3.392534] thunderbolt 0000:c4:00.5: deactivating PCIe Up path from 0:5
>> to 2:9
>> [    3.392539] thunderbolt 0000:c4:00.5: 0:5: deactivating_hop port = 5
>> hop_index=8
>> [    3.392637] thunderbolt 0000:c4:00.5: 2:1: deactivating_hop port = 1
>> hop_index=10
>> [    3.392799] thunderbolt 0-2: device disconnected
>>
>> But it seems like we are not cleaning up all the paths ?
> To me this looks correct and even your dmesg the PCIe tunnel that gets
> established after the "reset" seems to be working just fine. I also see
> that in your log you are doing the discovery before reset even though
> the original idea was to avoid it.
I did this as an experiment to collect logs and check if we are 
resetting the same
path config. Just to get a comparison view.
>
> In any case this was a good experiment. I will see if I can get this
> working on my side if I have some spare time during holidays.
Sure. I'll keep trying too.
> I guess we can to with the discovery but taking into account the
> "host_reset".
Yes, along with changes in lc.c for <= TBT3
> One additional question though, say we have PCIe tunnel established by
> the BIOS CM and we do the "reset", that means there will be hot-remove
> on the PCIe side and then hotplug again, does this slow down the boot
> considerably? We have some delays there in the PCIe code that might hit
> us here although I agree that we definitely prefer working system rather
> than fast-booting non-working system but perhaps the delays are not
> noticeable by the end-user?
I've not observed any delay which is noticeable. As soon as I get the 
login screen
and check dmesg, it would already be enumerated.

And moreover, this scenario is applicable only when dock stays connected 
during reboot or S5.