+Vibhore & Vishal
On 05/08/2024 11:58, Théo Lebrun wrote:
> Hello Roger,
>
> On Sat Aug 3, 2024 at 5:14 PM CEST, Roger Quadros wrote:
>> On 26/07/2024 21:17, Théo Lebrun wrote:
>>> Currently, system-wide suspend is broken on J7200 because of a
>>> controller reset. The TI wrapper does not get re-initialised at resume
>>> and the first register access from cdns core fails.
>>>
>>> We address that in a few ways:
>>> - In cdns3-ti, if a reset has occured at resume, we reconfigure the HW.
>>> - We pass the XHCI_RESET_ON_RESUME quirk, meaning the XHCI core expects
>>> a resume.
>>
>> OK.
>>> - We add a xhci->lost_power flag.
>>
>> Why?
>>
>>>
>>> The previous revision had one big issue: we had to know if
>>> reset-on-resume was true, at probe-time. This is where the main
>>
>> Don't we already know this at probe-time? why not just rely on the existing
>> XHCI_RESET_ON_RESUME qurik, than add a new mechanism?
>
> Some TI platforms cannot tell, before going to suspend, if their USB
> controller will reset. Suspend behavior is defined by (at least) two
> features:
>
> - Power domains. See arch/arm64/boot/dts/ti/k3-j7200-main.dtsi:
>
> usbss0: cdns-usb@4104000 {
> compatible = "ti,j7200-usb", "ti,j721e-usb";
> // ...
> power-domains = <&k3_pds 288 TI_SCI_PD_EXCLUSIVE>;
> // ...
> };
>
> This `power-domains` property implies that even s2idle will reset
> the controller.
I'm not so sure. All K3 platforms have the power-domains property for
the USB wrapper nodes.
>
> - Deep suspend. The type of suspend defines what will happen to various
> controllers. Currently deep suspend is suspend-to-RAM, with the SoC
> being turned off.
>
> This might evolve over time with more complex rules: the chosen
> suspend behavior could depend on wakeup source and/or wakeup target
> latencies. That information might not be available to Linux, being
> decided upon by firmwares. We need to be able to resume successfully
> without being surprised by a reset.
>
Got it. Might be worth to mention this in the patch description.
> I am sorry the precise usecase wasn't clear from the get-go.
>
> Thanks,
>
> --
> Théo Lebrun, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>
--
cheers,
-roger
