Hi Sandeep,
> On Nov 16, 2018, at 16:21, Singh, Sandeep <Sandeep.Singh@xxxxxxx> wrote:
>
> From: Sandeep Singh <sandeep.singh@xxxxxxx>
>
> Occasionally AMD SNPS 3.0 xHC does not respond to
> CSS when set, also it does not flag anything on SRE and HCE
> to point the internal xHC errors on USBSTS register. This stalls
> the entire system wide suspend and there is no point in stalling
> just because of xHC CSS is not responding.
>
> To work around this problem, if the xHC does not flag
> anything on SRE and HCE, we can skip the CSS
> timeout and allow the system to continue the suspend. Once the
> system resume happens we can internally reset the controller
> using XHCI_RESET_ON_RESUME quirk.
What happens to the connected and suspended USB devices?
Do USB devices lose remote wakeup functionality when this happens?
>
> Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@xxxxxxx>
> Signed-off-by: Sandeep Singh <Sandeep.Singh@xxxxxxx>
> cc: Nehal Shah <Nehal-bakulchandra.Shah@xxxxxxx>
> ---
> drivers/usb/host/xhci-pci.c | 4 ++++
> drivers/usb/host/xhci.c | 25 +++++++++++++++++++++++++
> drivers/usb/host/xhci.h | 1 +
> 3 files changed, 30 insertions(+)
>
> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
> index 01c5705..72493c4 100644
> --- a/drivers/usb/host/xhci-pci.c
> +++ b/drivers/usb/host/xhci-pci.c
> @@ -139,6 +139,10 @@ static void xhci_pci_quirks(struct device *dev, struct xhci_hcd *xhci)
> pdev->device == 0x43bb))
> xhci->quirks |= XHCI_SUSPEND_DELAY;
>
> + if (pdev->vendor == PCI_VENDOR_ID_AMD &&
> + (pdev->device == 0x15e0 || pdev->device == 0x15e1))
> + xhci->quirks |= XHCI_SNPS_BROKEN_SUSPEND;
> +
> if (pdev->vendor == PCI_VENDOR_ID_AMD)
> xhci->quirks |= XHCI_TRUST_TX_LENGTH;
>
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 0420eef..965b503 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -970,6 +970,7 @@ int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
> unsigned int delay = XHCI_MAX_HALT_USEC;
> struct usb_hcd *hcd = xhci_to_hcd(xhci);
> u32 command;
> + u32 res;
>
> if (!hcd->state)
> return 0;
> @@ -1025,10 +1026,32 @@ int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
> writel(command, &xhci->op_regs->command);
> if (xhci_handshake(&xhci->op_regs->status,
> STS_SAVE, 0, 10 * 1000)) {
> + if (xhci->quirks & XHCI_SNPS_BROKEN_SUSPEND) {
> + /*
> + * AMD SNPS xHC 3.0 occasionally does not clear the
> + * SSS bit of USBSTS and when driver tries to poll
> + * to see if the xHC clears BIT(8) which never happens
> + * and driver assumes that controller is not responding
> + * and times out. To workaround this, its good to check
> + * if SRE and HCE bits are not set (as per xhci
> + * Section 5.4.2) and bypass the timeout.
> + */
> +
> + res = readl(&xhci->op_regs->status);
> + if (res & STS_SAVE) {
> + if (((res & STS_SRE) == 0) &&
> + ((res & STS_HCE) == 0)) {
> + xhci->quirks |= XHCI_RESET_ON_RESUME;
> + goto complete_suspend;
> + }
> + }
Maybe merge the two “ifs”? There are no other conditions to handle.
Kai-Heng
> + }
> +
> xhci_warn(xhci, "WARN: xHC save state timeout\n");
> spin_unlock_irq(&xhci->lock);
> return -ETIMEDOUT;
> }
> + complete_suspend:
> spin_unlock_irq(&xhci->lock);
>
> /*
> @@ -1213,6 +1236,8 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
> usb_hcd_poll_rh_status(xhci->shared_hcd);
> set_bit(HCD_FLAG_POLL_RH, &hcd->flags);
> usb_hcd_poll_rh_status(hcd);
> + if (xhci->quirks & XHCI_SNPS_BROKEN_SUSPEND)
> + xhci->quirks &= ~XHCI_RESET_ON_RESUME;
>
> return retval;
> }
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index bf0b369..eb99782 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1849,6 +1849,7 @@ struct xhci_hcd {
> #define XHCI_INTEL_USB_ROLE_SW BIT_ULL(31)
> #define XHCI_ZERO_64B_REGS BIT_ULL(32)
> #define XHCI_DEFAULT_PM_RUNTIME_ALLOW BIT_ULL(33)
> +#define XHCI_SNPS_BROKEN_SUSPEND BIT_ULL(34)
>
> unsigned int num_active_eps;
> unsigned int limit_active_eps;
> --
> 2.7.4
>
