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// 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/bitfield.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 &= 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, ®);
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
*
* Check whether the mode is actually supported by the device before enabling
* and return an error if not. Additionally determine 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 compatibility */
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, ®);
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 &= ~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);
}
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