On 13/12/2024 18:03, Théo Lebrun wrote: > On Thu Dec 12, 2024 at 1:37 PM CET, Roger Quadros wrote: >> On 10/12/2024 19:13, Théo Lebrun wrote: >>> The XHCI_RESET_ON_RESUME quirk allows wrappers to signal that they >>> expect a reset after resume. It is also used by some to enforce a XHCI >>> reset on resume (see needs-reset-on-resume DT prop). >>> >>> Some wrappers are unsure beforehands if they will reset. Add a mechanism >>> to signal *at resume* if power has been lost. Parent devices can set >>> this flag, that defaults to false. >>> >>> The XHCI_RESET_ON_RESUME quirk still triggers a runtime_pm_get() on the >>> controller. This is required as we do not know if a suspend will >>> trigger a reset, so the best guess is to avoid runtime PM. >>> >>> Signed-off-by: Théo Lebrun <theo.lebrun@xxxxxxxxxxx> >>> --- >>> drivers/usb/host/xhci.c | 3 ++- >>> drivers/usb/host/xhci.h | 6 ++++++ >>> 2 files changed, 8 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c >>> index 5ebde8cae4fc44cdb997b0f61314e309bda56c0d..ae2c8daa206a87da24d58a62b0a0485ebf68cdd6 100644 >>> --- a/drivers/usb/host/xhci.c >>> +++ b/drivers/usb/host/xhci.c >>> @@ -1017,7 +1017,8 @@ int xhci_resume(struct xhci_hcd *xhci, pm_message_t msg) >>> >>> spin_lock_irq(&xhci->lock); >>> >>> - if (hibernated || xhci->quirks & XHCI_RESET_ON_RESUME || xhci->broken_suspend) >>> + if (hibernated || xhci->quirks & XHCI_RESET_ON_RESUME || >>> + xhci->broken_suspend || xhci->lost_power) >>> reinit_xhc = true; >>> >>> if (!reinit_xhc) { >>> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h >>> index 4914f0a10cff42dbc1448dcf7908534d582c848e..32526df75925989d40cbe7d59a187c945f498a30 100644 >>> --- a/drivers/usb/host/xhci.h >>> +++ b/drivers/usb/host/xhci.h >>> @@ -1645,6 +1645,12 @@ struct xhci_hcd { >>> unsigned broken_suspend:1; >>> /* Indicates that omitting hcd is supported if root hub has no ports */ >>> unsigned allow_single_roothub:1; >>> + /* >>> + * Signal from upper stacks that we lost power during system-wide >>> + * suspend. Its default value is based on XHCI_RESET_ON_RESUME, meaning >>> + * it is safe for wrappers to not modify lost_power at resume. >>> + */ >>> + unsigned lost_power:1; >> >> I suppose this is private to XHCI driver and not legitimate to be accessed >> by another driver after HCD is instantiated? > > Yes it is private. > >> Doesn't access to xhci_hcd need to be serialized via xhci->lock? > > Good question. In theory maybe. In practice I don't see how > cdns_host_resume(), called by cdns_resume(), could clash with anything > else. I'll add that to be safe. > >> Just curious, what happens if you don't include patch 4 and 5? >> Is USB functionality still broken for you? > > No it works fine. Patches 4+5 are only there to avoid the below warning. > Logging "xHC error in resume" is a lie, so I want to avoid it. How is it a lie? The XHCI controller did loose its save/restore state during a PM operation. As far as XHCI is concerned this is an error. no? > >> Doesn't XHCI driver detect that power was lost and issue a reset in any case >> via the below code >> >> /* re-initialize the HC on Restore Error, or Host Controller Error */ >> if ((temp & (STS_SRE | STS_HCE)) && >> !(xhci->xhc_state & XHCI_STATE_REMOVING)) { >> reinit_xhc = true; >> if (!xhci->broken_suspend) >> xhci_warn(xhci, "xHC error in resume, USBSTS 0x%x, Reinit\n", temp); >> } >> >>> /* cached extended protocol port capabilities */ >>> struct xhci_port_cap *port_caps; >>> unsigned int num_port_caps; >>> > > I'll wait for your opinion on the [PATCH v6 2/5] email thread before > sending a new revision. Sorry for the delay. I'm not an expert in PM but will give my opinion there anyways. > > Thanks, > > -- > Théo Lebrun, Bootlin > Embedded Linux and Kernel engineering > https://bootlin.com > > -- cheers, -roger