[PATCH V5 1/5] PCI: Add TLP Processing Hints (TPH) support

Wei Huang
2024-09-16T20:51:28Z

Add support for PCIe TLP Processing Hints (TPH) support (see PCIe r6.2,
sec 6.17).

Add missing TPH register definitions in pci_regs.h, including the TPH
Requester capability register, TPH Requester control register, TPH
Completer capability, and the ST fields of MSI-X entry.

Introduce pcie_enable_tph() and pcie_disable_tph(), enabling drivers to
toggle TPH support and configure specific ST mode as needed. Also add a
new kernel parameter, "pci=notph", allowing users to disable TPH support
across the entire system.

Co-developed-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Co-developed-by: Paul Luse <paul.e.luse@linux.intel.com>
Signed-off-by: Paul Luse <paul.e.luse@linux.intel.com>
Co-developed-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
---
.../admin-guide/kernel-parameters.txt | 4 +
drivers/pci/pci.c | 4 +
drivers/pci/pci.h | 12 ++
drivers/pci/pcie/Kconfig | 11 +
drivers/pci/pcie/Makefile | 1 +
drivers/pci/pcie/tph.c | 199 ++++++++++++++++++
drivers/pci/probe.c | 1 +
include/linux/pci-tph.h | 21 ++
include/linux/pci.h | 7 +
include/uapi/linux/pci_regs.h | 38 +++-
10 files changed, 290 insertions(+), 8 deletions(-)
create mode 100644 drivers/pci/pcie/tph.c
create mode 100644 include/linux/pci-tph.h

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 09126bb8cc9f..8579d0fbcd33 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4617,6 +4617,10 @@
nomio [S390] Do not use MIO instructions.
norid [S390] ignore the RID field and force use of
one PCI domain per PCI function
+ notph [PCIE] If the PCIE_TPH kernel config parameter
+ is enabled, this kernel boot option can be used
+ to disable PCIe TLP Processing Hints support
+ system-wide.

pcie_aspm= [PCIE] Forcibly enable or ignore PCIe Active State Power
Management.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index ffaaca0978cb..b6f60f7476cc 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1813,6 +1813,7 @@ int pci_save_state(struct pci_dev *dev)
pci_save_dpc_state(dev);
pci_save_aer_state(dev);
pci_save_ptm_state(dev);
+ pci_save_tph_state(dev);
return pci_save_vc_state(dev);
}
EXPORT_SYMBOL(pci_save_state);
@@ -1917,6 +1918,7 @@ void pci_restore_state(struct pci_dev *dev)
pci_restore_vc_state(dev);
pci_restore_rebar_state(dev);
pci_restore_dpc_state(dev);
+ pci_restore_tph_state(dev);
pci_restore_ptm_state(dev);

pci_aer_clear_status(dev);
@@ -6869,6 +6871,8 @@ static int __init pci_setup(char *str)
pci_no_domains();
} else if (!strncmp(str, "noari", 5)) {
pcie_ari_disabled = true;
+ } else if (!strncmp(str, "notph", 5)) {
+ pci_no_tph();
} else if (!strncmp(str, "cbiosize=", 9)) {
pci_cardbus_io_size = memparse(str + 9, &str);
} else if (!strncmp(str, "cbmemsize=", 10)) {
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 79c8398f3938..8eeabbbfa137 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -571,6 +571,18 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)

#endif /* CONFIG_PCI_IOV */

+#ifdef CONFIG_PCIE_TPH
+void pci_restore_tph_state(struct pci_dev *dev);
+void pci_save_tph_state(struct pci_dev *dev);
+void pci_no_tph(void);
+void pci_tph_init(struct pci_dev *dev);
+#else
+static inline void pci_restore_tph_state(struct pci_dev *dev) { }
+static inline void pci_save_tph_state(struct pci_dev *dev) { }
+static inline void pci_no_tph(void) { }
+static inline void pci_tph_init(struct pci_dev *dev) { }
+#endif
+
#ifdef CONFIG_PCIE_PTM
void pci_ptm_init(struct pci_dev *dev);
void pci_save_ptm_state(struct pci_dev *dev);
diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
index 17919b99fa66..61e4bd16eaf1 100644
--- a/drivers/pci/pcie/Kconfig
+++ b/drivers/pci/pcie/Kconfig
@@ -155,3 +155,14 @@ config PCIE_EDR
the PCI Firmware Specification r3.2. Enable this if you want to
support hybrid DPC model which uses both firmware and OS to
implement DPC.
+
+config PCIE_TPH
+ bool "TLP Processing Hints"
+ depends on ACPI
+ default n
+ help
+ This option adds support for PCIe TLP Processing Hints (TPH).
+ TPH allows endpoint devices to provide optimization hints, such as
+ desired caching behavior, for requests that target memory space.
+ These hints, called Steering Tags, can empower the system hardware
+ to optimize the utilization of platform resources.
diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
index 6461aa93fe76..3542b42ea0b9 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_PCIE_PME) += pme.o
obj-$(CONFIG_PCIE_DPC) += dpc.o
obj-$(CONFIG_PCIE_PTM) += ptm.o
obj-$(CONFIG_PCIE_EDR) += edr.o
+obj-$(CONFIG_PCIE_TPH) += tph.o
diff --git a/drivers/pci/pcie/tph.c b/drivers/pci/pcie/tph.c
new file mode 100644
index 000000000000..1efd76c8dd30
--- /dev/null
+++ b/drivers/pci/pcie/tph.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TPH (TLP Processing Hints) support
+ *
+ * Copyright (C) 2024 Advanced Micro Devices, Inc.
+ * Eric Van Tassell <Eric.VanTassell@amd.com>
+ * Wei Huang <wei.huang2@amd.com>
+ */
+#include <linux/pci.h>
+#include <linux/pci-acpi.h>
+#include <linux/bitfield.h>
+#include <linux/msi.h>
+#include <linux/pci-tph.h>
+
+#include "../pci.h"
+
+/* System-wide TPH disabled */
+static bool pci_tph_disabled;
+
+static u8 get_st_modes(struct pci_dev *pdev)
+{
+ u32 reg;
+
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+ reg &= PCI_TPH_CAP_ST_NS | PCI_TPH_CAP_ST_IV | PCI_TPH_CAP_ST_DS;
+
+ return reg;
+}
+
+/* Return device's Root Port completer capability */
+static u8 get_rp_completer_type(struct pci_dev *pdev)
+{
+ struct pci_dev *rp;
+ u32 reg;
+ int ret;
+
+ rp = pcie_find_root_port(pdev);
+ if (!rp)
+ return 0;
+
+ ret = pcie_capability_read_dword(rp, PCI_EXP_DEVCAP2, &reg);
+ if (ret)
+ return 0;
+
+ return FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg);
+}
+
+/**
+ * pcie_disable_tph - Turn off TPH support for device
+ * @pdev: PCI device
+ *
+ * Return: none
+ */
+void pcie_disable_tph(struct pci_dev *pdev)
+{
+ if (!pdev->tph_cap)
+ return;
+
+ if (!pdev->tph_enabled)
+ return;
+
+ pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, 0);
+
+ pdev->tph_mode = 0;
+ pdev->tph_req_type = 0;
+ pdev->tph_enabled = 0;
+}
+EXPORT_SYMBOL(pcie_disable_tph);
+
+/**
+ * pcie_enable_tph - Enable TPH support for device using a specific ST mode
+ * @pdev: PCI device
+ * @mode: ST mode to enable. Current supported modes include:
+ *
+ * - PCI_TPH_ST_NS_MODE: NO ST Mode
+ * - PCI_TPH_ST_IV_MODE: Interrupt Vector Mode
+ * - PCI_TPH_ST_DS_MODE: Device Specific Mode
+ *
+ * Checks whether the mode is actually supported by the device before enabling
+ * and returns an error if not. Additionally determines what types of requests,
+ * TPH or extended TPH, can be issued by the device based on its TPH requester
+ * capability and the Root Port's completer capability.
+ *
+ * Return: 0 on success, otherwise negative value (-errno)
+ */
+int pcie_enable_tph(struct pci_dev *pdev, int mode)
+{
+ u32 reg;
+ u8 dev_modes;
+ u8 rp_req_type;
+
+ /* Honor "notph" kernel parameter */
+ if (pci_tph_disabled)
+ return -EINVAL;
+
+ if (!pdev->tph_cap)
+ return -EINVAL;
+
+ if (pdev->tph_enabled)
+ return -EBUSY;
+
+ /* Sanitize and check ST mode comptability */
+ mode &= PCI_TPH_CTRL_MODE_SEL_MASK;
+ dev_modes = get_st_modes(pdev);
+ if (!((1 << mode) & dev_modes))
+ return -EINVAL;
+
+ pdev->tph_mode = mode;
+
+ /* Get req_type supported by device and its Root Port */
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
+ if (FIELD_GET(PCI_TPH_CAP_EXT_TPH, reg))
+ pdev->tph_req_type = PCI_TPH_REQ_EXT_TPH;
+ else
+ pdev->tph_req_type = PCI_TPH_REQ_TPH_ONLY;
+
+ rp_req_type = get_rp_completer_type(pdev);
+
+ /* Final req_type is the smallest value of two */
+ pdev->tph_req_type = min(pdev->tph_req_type, rp_req_type);
+
+ if (pdev->tph_req_type == PCI_TPH_REQ_DISABLE)
+ return -EINVAL;
+
+ /* Write them into TPH control register */
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, &reg);
+
+ reg &= ~PCI_TPH_CTRL_MODE_SEL_MASK;
+ reg |= FIELD_PREP(PCI_TPH_CTRL_MODE_SEL_MASK, pdev->tph_mode);
+
+ reg &= ~PCI_TPH_CTRL_REQ_EN_MASK;
+ reg |= FIELD_PREP(PCI_TPH_CTRL_REQ_EN_MASK, pdev->tph_req_type);
+
+ pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, reg);
+
+ pdev->tph_enabled = 1;
+
+ return 0;
+}
+EXPORT_SYMBOL(pcie_enable_tph);
+
+void pci_restore_tph_state(struct pci_dev *pdev)
+{
+ struct pci_cap_saved_state *save_state;
+ u32 *cap;
+
+ if (!pdev->tph_cap)
+ return;
+
+ if (!pdev->tph_enabled)
+ return;
+
+ save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_TPH);
+ if (!save_state)
+ return;
+
+ /* Restore control register and all ST entries */
+ cap = &save_state->cap.data[0];
+ pci_write_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, *cap++);
+}
+
+void pci_save_tph_state(struct pci_dev *pdev)
+{
+ struct pci_cap_saved_state *save_state;
+ u32 *cap;
+
+ if (!pdev->tph_cap)
+ return;
+
+ if (!pdev->tph_enabled)
+ return;
+
+ save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_TPH);
+ if (!save_state)
+ return;
+
+ /* Save control register */
+ cap = &save_state->cap.data[0];
+ pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CTRL, cap++);
+}
+
+void pci_no_tph(void)
+{
+ pci_tph_disabled = true;
+
+ pr_info("PCIe TPH is disabled\n");
+}
+
+void pci_tph_init(struct pci_dev *pdev)
+{
+ u32 save_size;
+
+ pdev->tph_cap = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_TPH);
+ if (!pdev->tph_cap)
+ return;
+
+ save_size = sizeof(u32);
+ pci_add_ext_cap_save_buffer(pdev, PCI_EXT_CAP_ID_TPH, save_size);
+}
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index b14b9876c030..c74adcdee52b 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2498,6 +2498,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
pci_dpc_init(dev); /* Downstream Port Containment */
pci_rcec_init(dev); /* Root Complex Event Collector */
pci_doe_init(dev); /* Data Object Exchange */
+ pci_tph_init(dev); /* TLP Processing Hints */

pcie_report_downtraining(dev);
pci_init_reset_methods(dev);
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
new file mode 100644
index 000000000000..58654a334ffb
--- /dev/null
+++ b/include/linux/pci-tph.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * TPH (TLP Processing Hints)
+ *
+ * Copyright (C) 2024 Advanced Micro Devices, Inc.
+ * Eric Van Tassell <Eric.VanTassell@amd.com>
+ * Wei Huang <wei.huang2@amd.com>
+ */
+#ifndef LINUX_PCI_TPH_H
+#define LINUX_PCI_TPH_H
+
+#ifdef CONFIG_PCIE_TPH
+void pcie_disable_tph(struct pci_dev *pdev);
+int pcie_enable_tph(struct pci_dev *pdev, int mode);
+#else
+static inline void pcie_disable_tph(struct pci_dev *pdev) { }
+static inline int pcie_enable_tph(struct pci_dev *pdev, int mode)
+{ return -EINVAL; }
+#endif
+
+#endif /* LINUX_PCI_TPH_H */
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 4cf89a4b4cbc..6f05deb6a0bf 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -433,6 +433,7 @@ struct pci_dev {
unsigned int ats_enabled:1; /* Address Translation Svc */
unsigned int pasid_enabled:1; /* Process Address Space ID */
unsigned int pri_enabled:1; /* Page Request Interface */
+ unsigned int tph_enabled:1; /* TLP Processing Hints */
unsigned int is_managed:1; /* Managed via devres */
unsigned int is_msi_managed:1; /* MSI release via devres installed */
unsigned int needs_freset:1; /* Requires fundamental reset */
@@ -530,6 +531,12 @@ struct pci_dev {

/* These methods index pci_reset_fn_methods[] */
u8 reset_methods[PCI_NUM_RESET_METHODS]; /* In priority order */
+
+#ifdef CONFIG_PCIE_TPH
+ u16 tph_cap; /* TPH capability offset */
+ u8 tph_mode; /* TPH mode */
+ u8 tph_req_type; /* TPH requester type */
+#endif
};

static inline struct pci_dev *pci_physfn(struct pci_dev *dev)
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 94c00996e633..25af1976953c 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -340,7 +340,9 @@
#define PCI_MSIX_ENTRY_UPPER_ADDR 0x4 /* Message Upper Address */
#define PCI_MSIX_ENTRY_DATA 0x8 /* Message Data */
#define PCI_MSIX_ENTRY_VECTOR_CTRL 0xc /* Vector Control */
-#define PCI_MSIX_ENTRY_CTRL_MASKBIT 0x00000001
+#define PCI_MSIX_ENTRY_CTRL_MASKBIT 0x00000001 /* Mask Bit */
+#define PCI_MSIX_ENTRY_CTRL_ST_LOWER 0x00ff0000 /* ST Lower */
+#define PCI_MSIX_ENTRY_CTRL_ST_UPPER 0xff000000 /* ST Upper */

/* CompactPCI Hotswap Register */

@@ -657,6 +659,7 @@
#define PCI_EXP_DEVCAP2_ATOMIC_COMP64 0x00000100 /* 64b AtomicOp completion */
#define PCI_EXP_DEVCAP2_ATOMIC_COMP128 0x00000200 /* 128b AtomicOp completion */
#define PCI_EXP_DEVCAP2_LTR 0x00000800 /* Latency tolerance reporting */
+#define PCI_EXP_DEVCAP2_TPH_COMP_MASK 0x00003000 /* TPH completer support */
#define PCI_EXP_DEVCAP2_OBFF_MASK 0x000c0000 /* OBFF support mechanism */
#define PCI_EXP_DEVCAP2_OBFF_MSG 0x00040000 /* New message signaling */
#define PCI_EXP_DEVCAP2_OBFF_WAKE 0x00080000 /* Re-use WAKE# for OBFF */
@@ -1020,15 +1023,34 @@
#define PCI_DPA_CAP_SUBSTATE_MASK 0x1F /* # substates - 1 */
#define PCI_DPA_BASE_SIZEOF 16 /* size with 0 substates */

+/* TPH Completer Support */
+#define PCI_EXP_DEVCAP2_TPH_COMP_NONE 0x0 /* None */
+#define PCI_EXP_DEVCAP2_TPH_COMP_TPH_ONLY 0x1 /* TPH only */
+#define PCI_EXP_DEVCAP2_TPH_COMP_EXT_TPH 0x3 /* TPH and Extended TPH */
+
/* TPH Requester */
#define PCI_TPH_CAP 4 /* capability register */
-#define PCI_TPH_CAP_LOC_MASK 0x600 /* location mask */
-#define PCI_TPH_LOC_NONE 0x000 /* no location */
-#define PCI_TPH_LOC_CAP 0x200 /* in capability */
-#define PCI_TPH_LOC_MSIX 0x400 /* in MSI-X */
-#define PCI_TPH_CAP_ST_MASK 0x07FF0000 /* ST table mask */
-#define PCI_TPH_CAP_ST_SHIFT 16 /* ST table shift */
-#define PCI_TPH_BASE_SIZEOF 0xc /* size with no ST table */
+#define PCI_TPH_CAP_ST_NS 0x00000001 /* No ST Mode Supported */
+#define PCI_TPH_CAP_ST_IV 0x00000002 /* Interrupt Vector Mode Supported */
+#define PCI_TPH_CAP_ST_DS 0x00000004 /* Device Specific Mode Supported */
+#define PCI_TPH_CAP_EXT_TPH 0x00000100 /* Ext TPH Requester Supported */
+#define PCI_TPH_CAP_LOC_MASK 0x00000600 /* ST Table Location */
+#define PCI_TPH_LOC_NONE 0x00000000 /* Not present */
+#define PCI_TPH_LOC_CAP 0x00000200 /* In capability */
+#define PCI_TPH_LOC_MSIX 0x00000400 /* In MSI-X */
+#define PCI_TPH_CAP_ST_MASK 0x07FF0000 /* ST Table Size */
+#define PCI_TPH_CAP_ST_SHIFT 16 /* ST Table Size shift */
+#define PCI_TPH_BASE_SIZEOF 0xc /* Size with no ST table */
+
+#define PCI_TPH_CTRL 8 /* control register */
+#define PCI_TPH_CTRL_MODE_SEL_MASK 0x00000007 /* ST Mode Select */
+#define PCI_TPH_ST_NS_MODE 0x0 /* No ST Mode */
+#define PCI_TPH_ST_IV_MODE 0x1 /* Interrupt Vector Mode */
+#define PCI_TPH_ST_DS_MODE 0x2 /* Device Specific Mode */
+#define PCI_TPH_CTRL_REQ_EN_MASK 0x00000300 /* TPH Requester Enable */
+#define PCI_TPH_REQ_DISABLE 0x0 /* No TPH requests allowed */
+#define PCI_TPH_REQ_TPH_ONLY 0x1 /* TPH only requests allowed */
+#define PCI_TPH_REQ_EXT_TPH 0x3 /* Extended TPH requests allowed */

/* Downstream Port Containment */
#define PCI_EXP_DPC_CAP 0x04 /* DPC Capability */
--
2.45.1