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

Alejandro Lucero Palau
2024-09-23T12:08:03Z

On 9/16/24 21:50, Wei Huang wrote:
> 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))

This is wrong. The mode definition is about the bit on and not about bit
position. You got this right in v4 ...

> + 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 */