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Message-ID: <63e848ea-3694-fef1-fab0-8c17000a3581@linux.intel.com>
Date: Tue, 20 Nov 2018 16:42:34 +0200
From: Mathias Nyman <mathias.nyman@...ux.intel.com>
To: Kai Heng Feng <kai.heng.feng@...onical.com>,
"Singh, Sandeep" <Sandeep.Singh@....com>
Cc: "mathias.nyman@...el.com" <mathias.nyman@...el.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"S-k, Shyam-sundar" <Shyam-sundar.S-k@....com>,
"Shah, Nehal-bakulchandra" <Nehal-bakulchandra.Shah@....com>
Subject: Re: [PATCH] xhci: workaround CSS timeout on AMD SNPS 3.0 xHC.
On 16.11.2018 10:35, Kai Heng Feng wrote:
> Hi Sandeep,
>
>> On Nov 16, 2018, at 16:21, Singh, Sandeep <Sandeep.Singh@....com> wrote:
>>
>> From: Sandeep Singh <sandeep.singh@....com>
>>
>> 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@....com>
>> Signed-off-by: Sandeep Singh <Sandeep.Singh@....com>
>> cc: Nehal Shah <Nehal-bakulchandra.Shah@....com>
>> ---
>> 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;
Better to use some other way or variable, after this change quirks would become dynamic,
and depend on each other.
>> + goto complete_suspend;
>> + }
>> + }
>
> Maybe merge the two “ifs”? There are no other conditions to handle.
>> Kai-Heng
Or drop the if (res & STS_SAVE) check completely.
Only reason we are here is because STS_SAVE is still set.
I think the goto statement is not needed either, how about something like
if (BROKEN_SUSPEND_QUIRK && !(SRE || HCE))
set some reset on resume flag
else
unlock
return -ETIMEDOUT
>
>> + }
>> +
>> 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;
Again, I don't think its a good idea to create this kind of quirk dependency,
what about if a future controller needs both SNPS_BROKEN_SUSPEND and
always a RESET_ON_RESUME?
-Mathias
>>
>> 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
>>
>
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