[PATCH RFC v2 1/4] PCI: hotplug: Add support for disabling in-band presence

Alexandru Gagniuc
2019-02-20T01:20:53Z

The presence detect state (PDS) is normally a logical or of in-band
and out-of-band presence. In PCIe 4.0, there is the option to disable
in-band presence so that the PDS bit always reflects the state of the
out-of-band presence.

The recommendation of the PCIe spec is to disable in-band presence
whenever supported.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
---
drivers/pci/hotplug/pciehp.h | 1 +
drivers/pci/hotplug/pciehp_hpc.c | 12 +++++++++++-
include/linux/pci.h | 1 +
include/uapi/linux/pci_regs.h | 2 ++
4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index 506e1d923a1f..6f729ce4a7b9 100644
--- a/drivers/pci/hotplug/pciehp.h
+++ b/drivers/pci/hotplug/pciehp.h
@@ -98,6 +98,7 @@ struct controller {
struct pcie_device *pcie;

u32 slot_cap; /* capabilities and quirks */
+ unsigned int inband_presence_disabled:1;

u16 slot_ctrl; /* control register access */
struct mutex ctrl_lock;
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 7dd443aea5a5..f77dc7c38f9a 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -824,7 +824,7 @@ static inline void dbg_ctrl(struct controller *ctrl)
struct controller *pcie_init(struct pcie_device *dev)
{
struct controller *ctrl;
- u32 slot_cap, link_cap;
+ u32 slot_cap, slot_cap2, link_cap;
u8 poweron;
struct pci_dev *pdev = dev->port;
struct pci_bus *subordinate = pdev->subordinate;
@@ -846,6 +846,9 @@ struct controller *pcie_init(struct pcie_device *dev)
if (pdev->is_thunderbolt)
slot_cap |= PCI_EXP_SLTCAP_NCCS;

+ if (pdev->no_in_band_presence)
+ ctrl->inband_presence_disabled = 1;
+
ctrl->slot_cap = slot_cap;
mutex_init(&ctrl->ctrl_lock);
mutex_init(&ctrl->state_lock);
@@ -882,6 +885,13 @@ struct controller *pcie_init(struct pcie_device *dev)
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 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/linux/pci.h b/include/linux/pci.h
index 65f1d8c2f082..9d08cdbca459 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -413,6 +413,7 @@ struct pci_dev {
unsigned int non_compliant_bars:1; /* Broken BARs; ignore them */
unsigned int is_probed:1; /* Device probing in progress */
unsigned int link_active_reporting:1;/* Device capable of reporting link active */
+ unsigned int no_in_band_presence:1; /* Device does not report in-band presence */
unsigned int no_vf_scan:1; /* Don't scan for VFs after IOV enablement */
pci_dev_flags_t dev_flags;
atomic_t enable_cnt; /* pci_enable_device has been called */
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index e1e9888c85e6..5423dc476c77 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -597,6 +597,7 @@
#define PCI_EXP_SLTCTL_PWR_OFF 0x0400 /* Power Off */
#define PCI_EXP_SLTCTL_EIC 0x0800 /* Electromechanical Interlock Control */
#define PCI_EXP_SLTCTL_DLLSCE 0x1000 /* Data Link Layer State Changed Enable */
+#define PCI_EXP_SLTCTL_IBPD_DISABLE 0x4000 /* In-band PD disable */
#define PCI_EXP_SLTSTA 26 /* Slot Status */
#define PCI_EXP_SLTSTA_ABP 0x0001 /* Attention Button Pressed */
#define PCI_EXP_SLTSTA_PFD 0x0002 /* Power Fault Detected */
@@ -667,6 +668,7 @@
#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_SLTCTL2 56 /* Slot Control 2 */
#define PCI_EXP_SLTSTA2 58 /* Slot Status 2 */

--
2.19.2