Re: [RFC PATCH] USB: xhci: Enable HCE event reset function

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Nov 18, 2020 at 05:04:36PM +0800, liulongfang wrote:
> On 2020/11/18 15:02, Greg KH Wrote:
> > On Wed, Nov 18, 2020 at 11:36:13AM +0800, Longfang Liu wrote:
> >> The HCE(Host Controller Error) event has been defined in
> >> the XHCI driver but has not been used. If we want to use
> >> the HCE event to reset the controller, can we implement
> >> it in the interrupt function as follows:
> >>
> >> xhci_irq()
> >>     |----xhci_halt()
> >>     |----xhci_shutdown()
> >>     |----xhci_start()
> >>     |----xhci_run()
> >>
> >> Signed-off-by: Longfang Liu <liulongfang@huawei.com>
> >> ---
> >>  drivers/usb/host/xhci-ring.c | 10 ++++++++++
> >>  1 file changed, 10 insertions(+)
> > 
> > $ ./scripts/get_maintainer.pl --file drivers/usb/host/xhci-ring.c
> > Mathias Nyman <mathias.nyman@intel.com> (supporter:USB XHCI DRIVER)
> > Greg Kroah-Hartman <gregkh@linuxfoundation.org> (supporter:USB SUBSYSTEM)
> > linux-usb@vger.kernel.org (open list:USB XHCI DRIVER)
> > linux-kernel@vger.kernel.org (open list)
> > 
> > Any reason to not include the maintainer of the xhci driver here?
> OK, I will include the maintainer in the next patch.
> > 
> >> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> >> index 2c255d0..87b3a40 100644
> >> --- a/drivers/usb/host/xhci-ring.c
> >> +++ b/drivers/usb/host/xhci-ring.c
> >> @@ -2857,6 +2857,16 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
> >>  		goto out;
> >>  	}
> >>  
> >> +	if (status & STS_HCE) {
> >> +		xhci_warn(xhci, "WARNING: Host Controller Error\n");
> >> +		xhci_halt(xhci);
> >> +		xhci_shutdown(hcd);
> >> +		xhci_start(xhci);
> >> +		xhci_run(hcd);
> >> +		ret = IRQ_HANDLED;
> >> +		goto out;
> >> +	}
> >> +
> > 
> > Does this fix a real problem for you?  Are you sure we will not suddenly
> > start resetting devices that were working properly and sending this
> > error incorrectly?  How did you test this?
> > 
> > thanks,
> > 
> > greg k-h
> > .
> > 
> Yes, we want to add a RAS feature to the USB,

What is "RAS"?

> Use the HCE event to trigger the reset operation of the USB controller.

Is that allowed by the XHCI specification?

> By searching for the current xhci driver, the driver did not handle HCE event.
> In fact, I am not sure if other operations will cause HCE, The HCE event is
> used to reset the USB controller according to the definition of the event.

What generates that event?  Do existing controllers do that today?  What
causes it?

> I test this reset operation through the Sysfs file, but have not tested all usage scenarios.

What sysfs file?

thanks,

greg k-h