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Message-ID: <4e54e701-223d-f202-9da7-0f2849a53555@amd.com>
Date: Fri, 23 Nov 2018 14:39:09 +0000
From: Sandeep Singh <ssingh1@....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 v2] xhci: workaround CSS timeout on AMD SNPS 3.0 xHC
Hi Kai-heng,
On 11/23/2018 2:59 PM, Kai Heng Feng wrote:
> Hi Sandeep,
>
>> On Nov 22, 2018, at 12:23 PM, 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
>>
>> 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>
>> ---
>> Changes since v1:
>>
>> -> New Variable based decision making when SNPS issue happens hence
>> quirk interdependency removed.
>> -> Removed STS conditional check in suspend function.
>>
>> drivers/usb/host/xhci-pci.c | 4 ++++
>> drivers/usb/host/xhci.c | 26 ++++++++++++++++++++++----
>> drivers/usb/host/xhci.h | 3 +++
>> 3 files changed, 29 insertions(+), 4 deletions(-)
>>
>> 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..808677d 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;
>> @@ -1023,11 +1024,28 @@ int xhci_suspend(struct xhci_hcd *xhci, bool do_wakeup)
>> command = readl(&xhci->op_regs->command);
>> command |= CMD_CSS;
>> writel(command, &xhci->op_regs->command);
>> + xhci->broken_suspend = 0;
>> if (xhci_handshake(&xhci->op_regs->status,
>> STS_SAVE, 0, 10 * 1000)) {
>> - xhci_warn(xhci, "WARN: xHC save state timeout\n");
>> - spin_unlock_irq(&xhci->lock);
>> - return -ETIMEDOUT;
>> + /*
>> + * 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 ((xhci->quirks & XHCI_SNPS_BROKEN_SUSPEND) &&
>> + (((res & STS_SRE) == 0) &&
>> + ((res & STS_HCE) == 0))) {
>> + xhci->broken_suspend = 1;
>> + } else {
>> + xhci_warn(xhci, "WARN: xHC save state timeout\n");
>> + spin_unlock_irq(&xhci->lock);
>> + return -ETIMEDOUT;
>> + }
>> }
>> spin_unlock_irq(&xhci->lock);
>>
>> @@ -1080,7 +1098,7 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
>> set_bit(HCD_FLAG_HW_ACCESSIBLE, &xhci->shared_hcd->flags);
>>
>> spin_lock_irq(&xhci->lock);
>> - if (xhci->quirks & XHCI_RESET_ON_RESUME)
>> + if ((xhci->quirks & XHCI_RESET_ON_RESUME) || xhci->broken_suspend)
>> hibernated = true;
>>
>> if (!hibernated) {
>> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
>> index bf0b369..d5d19b2 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)
>
> This bit is already in use by a another patch, so please update its value.
Thanks for addressing we will be sending patch v3.
>
> Kai-Heng
>
>>
>> unsigned int num_active_eps;
>> unsigned int limit_active_eps;
>> @@ -1878,6 +1879,8 @@ struct xhci_hcd {
>> void *dbc;
>> /* platform-specific data -- must come last */
>> unsigned long priv[0] __aligned(sizeof(s64));
>> + /* Broken Suspend flag for SNPS Suspend resume issue */
>> + u8 broken_suspend;
>> };
>>
>> /* Platform specific overrides to generic XHCI hc_driver ops */
>> --
>> 2.7.4
>>
>
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