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Message-ID: <20180507213344.GA133147@bhelgaas-glaptop.roam.corp.google.com>
Date: Mon, 7 May 2018 16:33:44 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: okaya@...eaurora.org
Cc: Paul Menzel <pmenzel+linux-pci@...gen.mpg.de>,
Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, Lukas Wunner <lukas@...ner.de>
Subject: Re: pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038
(issued 65284 msec ago)
On Fri, May 04, 2018 at 08:33:27AM -0500, Bjorn Helgaas wrote:
> commit b0d6f2230e12c85ae3b65a854a53c67c7c1f6406
> Author: Bjorn Helgaas <bhelgaas@...gle.com>
> Date: Thu May 3 18:39:38 2018 -0500
>
> PCI: pciehp: Add quirk for Intel Command Completed erratum
>
> The Intel CF118 erratum means the controller does not set the Command
> Completed bit unless writes to the Slot Command register change "Control"
> bits. Command Completed is never set for writes that only change software
> notification "Enable" bits. This results in timeouts like this:
>
> pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago)
>
> When this erratum is present, avoid these timeouts by marking commands
> "completed" immediately unless they change the "Control" bits.
>
> Here's the text of the erratum from the Intel document:
>
> CF118 PCIe Slot Status Register Command Completed bit not always
> updated on any configuration write to the Slot Control
> Register
>
> Problem: For PCIe root ports (devices 0 - 10) supporting hot-plug,
> the Slot Status Register (offset AAh) Command Completed
> (bit[4]) status is updated under the following condition:
> IOH will set Command Completed bit after delivering the new
> commands written in the Slot Controller register (offset
> A8h) to VPP. The IOH detects new commands written in Slot
> Control register by checking the change of value for Power
> Controller Control (bit[10]), Power Indicator Control
> (bits[9:8]), Attention Indicator Control (bits[7:6]), or
> Electromechanical Interlock Control (bit[11]) fields. Any
> other configuration writes to the Slot Control register
> without changing the values of these fields will not cause
> Command Completed bit to be set.
>
> The PCIe Base Specification Revision 2.0 or later describes
> the “Slot Control Register” in section 7.8.10, as follows
> (Reference section 7.8.10, Slot Control Register, Offset
> 18h). In hot-plug capable Downstream Ports, a write to the
> Slot Control register must cause a hot-plug command to be
> generated (see Section 6.7.3.2 for details on hot-plug
> commands). A write to the Slot Control register in a
> Downstream Port that is not hotplug capable must not cause a
> hot-plug command to be executed.
>
> The PCIe Spec intended that every write to the Slot Control
> Register is a command and expected a command complete status
> to abstract the VPP implementation specific nuances from the
> OS software. IOH PCIe Slot Control Register implementation
> is not fully conforming to the PCIe Specification in this
> respect.
>
> Implication: Software checking on the Command Completed status after
> writing to the Slot Control register may time out.
>
> Workaround: Software can read the Slot Control register and compare the
> existing and new values to determine if it should check the
> Command Completed status after writing to the Slot Control
> register.
>
> Link: http://www.intel.com/content/www/us/en/processors/xeon/xeon-e7-v2-spec-update.html
> Link: https://lkml.kernel.org/r/8770820b-85a0-172b-7230-3a44524e6c9f@molgen.mpg.de
> Reported-by: Paul Menzel <pmenzel+linux-pci@...gen.mpg.de>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
I applied this with Paul's tested-by on pci/hotplug for v4.18.
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 18a42f8f5dc5..e70eba5ea906 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -10,7 +10,6 @@
> * All rights reserved.
> *
> * Send feedback to <greg@...ah.com>,<kristen.c.accardi@...el.com>
> - *
> */
>
> #include <linux/kernel.h>
> @@ -147,25 +146,22 @@ static void pcie_wait_cmd(struct controller *ctrl)
> else
> rc = pcie_poll_cmd(ctrl, jiffies_to_msecs(timeout));
>
> - /*
> - * Controllers with errata like Intel CF118 don't generate
> - * completion notifications unless the power/indicator/interlock
> - * control bits are changed. On such controllers, we'll emit this
> - * timeout message when we wait for completion of commands that
> - * don't change those bits, e.g., commands that merely enable
> - * interrupts.
> - */
> if (!rc)
> ctrl_info(ctrl, "Timeout on hotplug command %#06x (issued %u msec ago)\n",
> ctrl->slot_ctrl,
> jiffies_to_msecs(jiffies - ctrl->cmd_started));
> }
>
> +#define CC_ERRATUM_MASK (PCI_EXP_SLTCTL_PCC | \
> + PCI_EXP_SLTCTL_PIC | \
> + PCI_EXP_SLTCTL_AIC | \
> + PCI_EXP_SLTCTL_EIC)
> +
> static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
> u16 mask, bool wait)
> {
> struct pci_dev *pdev = ctrl_dev(ctrl);
> - u16 slot_ctrl;
> + u16 slot_ctrl_orig, slot_ctrl;
>
> mutex_lock(&ctrl->ctrl_lock);
>
> @@ -180,6 +176,7 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
> goto out;
> }
>
> + slot_ctrl_orig = slot_ctrl;
> slot_ctrl &= ~mask;
> slot_ctrl |= (cmd & mask);
> ctrl->cmd_busy = 1;
> @@ -188,6 +185,17 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
> ctrl->cmd_started = jiffies;
> ctrl->slot_ctrl = slot_ctrl;
>
> + /*
> + * Controllers with the Intel CF118 and similar errata advertise
> + * Command Completed support, but they only set Command Completed
> + * if we change the "Control" bits for power, power indicator,
> + * attention indicator, or interlock. If we only change the
> + * "Enable" bits, they never set the Command Completed bit.
> + */
> + if (pdev->broken_cmd_compl &&
> + (slot_ctrl_orig & CC_ERRATUM_MASK) == (slot_ctrl & CC_ERRATUM_MASK))
> + ctrl->cmd_busy = 0;
> +
> /*
> * Optionally wait for the hardware to be ready for a new command,
> * indicating completion of the above issued command.
> @@ -861,7 +869,7 @@ struct controller *pcie_init(struct pcie_device *dev)
> PCI_EXP_SLTSTA_MRLSC | PCI_EXP_SLTSTA_CC |
> PCI_EXP_SLTSTA_DLLSC);
>
> - ctrl_info(ctrl, "Slot #%d AttnBtn%c PwrCtrl%c MRL%c AttnInd%c PwrInd%c HotPlug%c Surprise%c Interlock%c NoCompl%c LLActRep%c\n",
> + ctrl_info(ctrl, "Slot #%d AttnBtn%c PwrCtrl%c MRL%c AttnInd%c PwrInd%c HotPlug%c Surprise%c Interlock%c NoCompl%c LLActRep%c%s\n",
> (slot_cap & PCI_EXP_SLTCAP_PSN) >> 19,
> FLAG(slot_cap, PCI_EXP_SLTCAP_ABP),
> FLAG(slot_cap, PCI_EXP_SLTCAP_PCP),
> @@ -872,7 +880,8 @@ struct controller *pcie_init(struct pcie_device *dev)
> FLAG(slot_cap, PCI_EXP_SLTCAP_HPS),
> FLAG(slot_cap, PCI_EXP_SLTCAP_EIP),
> FLAG(slot_cap, PCI_EXP_SLTCAP_NCCS),
> - FLAG(link_cap, PCI_EXP_LNKCAP_DLLLARC));
> + FLAG(link_cap, PCI_EXP_LNKCAP_DLLLARC),
> + pdev->broken_cmd_compl ? " (with Cmd Compl erratum)" : "");
>
> if (pcie_init_slot(ctrl))
> goto abort_ctrl;
> @@ -891,3 +900,17 @@ void pciehp_release_ctrl(struct controller *ctrl)
> pcie_cleanup_slot(ctrl);
> kfree(ctrl);
> }
> +
> +static void quirk_cmd_compl(struct pci_dev *pdev)
> +{
> + u32 slot_cap;
> +
> + if (pci_is_pcie(pdev)) {
> + pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP, &slot_cap);
> + if (slot_cap & PCI_EXP_SLTCAP_HPC &&
> + !(slot_cap & PCI_EXP_SLTCAP_NCCS))
> + pdev->broken_cmd_compl = 1;
> + }
> +}
> +DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_INTEL, PCI_ANY_ID,
> + PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 73178a2fcee0..60cb5350ad28 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -406,6 +406,9 @@ struct pci_dev {
> struct bin_attribute *res_attr[DEVICE_COUNT_RESOURCE]; /* sysfs file for resources */
> struct bin_attribute *res_attr_wc[DEVICE_COUNT_RESOURCE]; /* sysfs file for WC mapping of resources */
>
> +#ifdef CONFIG_HOTPLUG_PCI_PCIE
> + unsigned int broken_cmd_compl:1; /* Command Complete broken */
> +#endif
> #ifdef CONFIG_PCIE_PTM
> unsigned int ptm_root:1;
> unsigned int ptm_enabled:1;
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