Re: [PATCH v4 0/3] PCI: pciehp: Do not turn off slot if presence comes up after link
From: Bjorn Helgaas
Date: Mon Feb 10 2020 - 19:08:20 EST
[+cc Libor (thanks for the ping!)]
On Fri, Oct 25, 2019 at 03:00:44PM -0400, Stuart Hayes wrote:
> In older PCIe specs, PDS (presence detect) would come up when the
> "in-band" presence detect pin connected, and would be up before DLLLA
> (link active).
>
> In PCIe 4.0 (as an ECN) and in PCIe 5.0, there is a new bit to show if
> in-band presence detection can be disabled for the slot, and another bit
> that disables it--and a recommendation that it should be disabled if it
> can be. In addition, certain OEMs disable in-band presence detection
> without implementing these bits.
>
> This means it is possible to get a "card present" interrupt after the
> link is up and the driver is loaded. This causes an erroneous removal
> of the device driver, followed by an immediate re-probing.
>
> This patch set defines these new bits, uses them to disable in-band
> presence detection if it can be, waits for PDS to go up if in-band
> presence detection is disabled, and adds a DMI table that will let us
> know if we should assume in-band presence is disabled on a system.
>
> The first two patches in this set come from a patch set that was
> submitted but not accepted many months ago by Alexandru Gagniuc [1].
> The first is unmodified, the second has the commit message and timeout
> modified.
>
> [1] https://patchwork.kernel.org/cover/10909167/
> [v3,0/4] PCI: pciehp: Do not turn off slot if presence comes up after link
>
> v2:
> - modify loop in pcie_wait_for_presence to do..while
>
> v3:
> - remove unused variable declaration
> - modify text of warning message
>
> v4:
> - remove "!!" boolean conversion in an "if" condition for readability
> - add explanation comment in dmi table
>
> Alexandru Gagniuc (2):
> PCI: pciehp: Add support for disabling in-band presence
> PCI: pciehp: Wait for PDS if in-band presence is disabled
>
> Stuart Hayes (1):
> PCI: pciehp: Add dmi table for in-band presence disabled
>
> drivers/pci/hotplug/pciehp.h | 1 +
> drivers/pci/hotplug/pciehp_hpc.c | 50 +++++++++++++++++++++++++++++++-
> include/uapi/linux/pci_regs.h | 2 ++
> 3 files changed, 52 insertions(+), 1 deletion(-)
I added the spec reference to the 1/3 commit log, tried to make the
tweaks Lukas suggested (interdiff below), used ctrl_info() instead of
pci_info() (I would actually like to change the whole driver to use
pci_info(), but better to be consistent for now), and applied to
pci/hotplug for v5.7.
Somebody should also update lspci to:
- Do something with DevCap AttnBtn, AttnInd, PwrInd to indicate that
they were only defined for PCIe r1.0 and have been explicitly
undefined since then. If there's a way to identify those 1.0
devices and only decode those fields for 1.0, that would be nice.
- Add SltCap2 and SltCtrl2 decoding.
Speak up if you plan to do this so we don't duplicate effort.
Bjorn
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index ae0108b92084..469873b44a8e 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -284,7 +284,7 @@ static void pcie_wait_for_presence(struct pci_dev *pdev)
timeout -= 10;
} while (timeout > 0);
- pci_info(pdev, "Timeout waiting for Presence Detect state to be set\n");
+ ctrl_info(ctrl, "Timeout waiting for Presence Detect\n");
}
int pciehp_check_link_status(struct controller *ctrl)
@@ -921,6 +921,16 @@ struct controller *pcie_init(struct pcie_device *dev)
ctrl->state = list_empty(&subordinate->devices) ? OFF_STATE : ON_STATE;
up_read(&pci_bus_sem);
+ pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP2, &slot_cap2);
+ if (slot_cap2 & PCI_EXP_SLTCAP2_IBPD) {
+ pcie_write_cmd_nowait(ctrl, PCI_EXP_SLTCTL_IBPD_DISABLE,
+ PCI_EXP_SLTCTL_IBPD_DISABLE);
+ ctrl->inband_presence_disabled = 1;
+ }
+
+ if (dmi_first_match(inband_presence_disabled_dmi_table))
+ ctrl->inband_presence_disabled = 1;
+
/* Check if Data Link Layer Link Active Reporting is implemented */
pcie_capability_read_dword(pdev, PCI_EXP_LNKCAP, &link_cap);
@@ -930,7 +940,7 @@ struct controller *pcie_init(struct pcie_device *dev)
PCI_EXP_SLTSTA_MRLSC | PCI_EXP_SLTSTA_CC |
PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC);
- 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",
+ ctrl_info(ctrl, "Slot #%d AttnBtn%c PwrCtrl%c MRL%c AttnInd%c PwrInd%c HotPlug%c Surprise%c Interlock%c NoCompl%c IbPresDis%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),
@@ -941,19 +951,10 @@ 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),
+ ctrl->inband_presence_disabled,
FLAG(link_cap, PCI_EXP_LNKCAP_DLLLARC),
pdev->broken_cmd_compl ? " (with Cmd Compl erratum)" : "");
- pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP2, &slot_cap2);
- if (slot_cap2 & PCI_EXP_SLTCAP2_IBPD) {
- pcie_write_cmd_nowait(ctrl, PCI_EXP_SLTCTL_IBPD_DISABLE,
- PCI_EXP_SLTCTL_IBPD_DISABLE);
- ctrl->inband_presence_disabled = 1;
- }
-
- if (dmi_first_match(inband_presence_disabled_dmi_table))
- ctrl->inband_presence_disabled = 1;
-
/*
* If empty slot's power status is on, turn power off. The IRQ isn't
* requested yet, so avoid triggering a notification with this command.
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index b464d2f76513..f9701410d3b5 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -681,7 +681,7 @@
#define PCI_EXP_LNKSTA2 50 /* Link Status 2 */
#define PCI_CAP_EXP_ENDPOINT_SIZEOF_V2 52 /* v2 endpoints with link end here */
#define PCI_EXP_SLTCAP2 52 /* Slot Capabilities 2 */
-#define PCI_EXP_SLTCAP2_IBPD 0x0001 /* In-band PD Disable Supported */
+#define PCI_EXP_SLTCAP2_IBPD 0x00000001 /* In-band PD Disable Supported */
#define PCI_EXP_SLTCTL2 56 /* Slot Control 2 */
#define PCI_EXP_SLTSTA2 58 /* Slot Status 2 */