[PATCH V2 3/9] PCI/TPH: Implement a command line option to disable TPH

From: Wei Huang
Date: Fri May 31 2024 - 17:40:15 EST

Provide a kernel option, with related helper functions, to completely
disable TPH so that no TPH headers are generated.

Co-developed-by: Eric Van Tassell <Eric.VanTassell@xxxxxxx>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@xxxxxxx>
Signed-off-by: Wei Huang <wei.huang2@xxxxxxx>
Reviewed-by: Ajit Khaparde <ajit.khaparde@xxxxxxxxxxxx>
Reviewed-by: Somnath Kotur <somnath.kotur@xxxxxxxxxxxx>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@xxxxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 1 +
drivers/pci/pci-driver.c | 7 ++++-
drivers/pci/pci.c | 12 ++++++++
drivers/pci/pcie/tph.c | 30 +++++++++++++++++++
include/linux/pci-tph.h | 19 ++++++++++++
include/linux/pci.h | 1 +
6 files changed, 69 insertions(+), 1 deletion(-)
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 500cfa776225..fedcc69e35c1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4623,6 +4623,7 @@
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] Do not use PCIe TPH

pcie_aspm= [PCIE] Forcibly enable or ignore PCIe Active State Power
Management.
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index af2996d0d17f..9722d070c0ca 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -21,6 +21,7 @@
#include <linux/acpi.h>
#include <linux/dma-map-ops.h>
#include <linux/iommu.h>
+#include <linux/pci-tph.h>
#include "pci.h"
#include "pcie/portdrv.h"

@@ -322,8 +323,12 @@ static long local_pci_probe(void *_ddi)
pm_runtime_get_sync(dev);
pci_dev->driver = pci_drv;
rc = pci_drv->probe(pci_dev, ddi->id);
- if (!rc)
+ if (!rc) {
+ if (pci_tph_disabled())
+ pcie_tph_disable(pci_dev);
+
return rc;
+ }
if (rc < 0) {
pci_dev->driver = NULL;
pm_runtime_put_sync(dev);
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 59e0949fb079..31c443504ce9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -157,6 +157,9 @@ static bool pcie_ari_disabled;
/* If set, the PCIe ATS capability will not be used. */
static bool pcie_ats_disabled;

+/* If set, the PCIe TPH capability will not be used. */
+static bool pcie_tph_disabled;
+
/* If set, the PCI config space of each device is printed during boot. */
bool pci_early_dump;

@@ -166,6 +169,12 @@ bool pci_ats_disabled(void)
}
EXPORT_SYMBOL_GPL(pci_ats_disabled);

+bool pci_tph_disabled(void)
+{
+ return pcie_tph_disabled;
+}
+EXPORT_SYMBOL_GPL(pci_tph_disabled);
+
/* Disable bridge_d3 for all PCIe ports */
static bool pci_bridge_d3_disable;
/* Force bridge_d3 for all PCIe ports */
@@ -6806,6 +6815,9 @@ static int __init pci_setup(char *str)
pci_no_domains();
} else if (!strncmp(str, "noari", 5)) {
pcie_ari_disabled = true;
+ } else if (!strcmp(str, "notph")) {
+ pr_info("PCIe: TPH is disabled\n");
+ pcie_tph_disabled = true;
} 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/pcie/tph.c b/drivers/pci/pcie/tph.c
index 5f0cc06b74bb..5dc533b89a33 100644
--- a/drivers/pci/pcie/tph.c
+++ b/drivers/pci/pcie/tph.c
@@ -16,11 +16,41 @@
#include <linux/errno.h>
#include <linux/msi.h>
#include <linux/pci.h>
+#include <linux/pci-tph.h>
#include <linux/msi.h>
#include <linux/pci-acpi.h>

#include "../pci.h"

+static int tph_set_reg_field_u32(struct pci_dev *dev, u8 offset, u32 mask,
+ u8 shift, u32 field)
+{
+ u32 reg_val;
+ int ret;
+
+ if (!dev->tph_cap)
+ return -EINVAL;
+
+ ret = pci_read_config_dword(dev, dev->tph_cap + offset, &reg_val);
+ if (ret)
+ return ret;
+
+ reg_val &= ~mask;
+ reg_val |= (field << shift) & mask;
+
+ ret = pci_write_config_dword(dev, dev->tph_cap + offset, reg_val);
+
+ return ret;
+}
+
+int pcie_tph_disable(struct pci_dev *dev)
+{
+ return tph_set_reg_field_u32(dev, PCI_TPH_CTRL,
+ PCI_TPH_CTRL_REQ_EN_MASK,
+ PCI_TPH_CTRL_REQ_EN_SHIFT,
+ PCI_TPH_REQ_DISABLE);
+}
+
void pcie_tph_init(struct pci_dev *dev)
{
dev->tph_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_TPH);
diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
new file mode 100644
index 000000000000..e187d7e89e8c
--- /dev/null
+++ b/include/linux/pci-tph.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * TPH (TLP Processing Hints)
+ *
+ * Copyright (C) 2024 Advanced Micro Devices, Inc.
+ * Eric Van Tassell <Eric.VanTassell@xxxxxxx>
+ * Wei Huang <wei.huang2@xxxxxxx>
+ */
+#ifndef LINUX_PCI_TPH_H
+#define LINUX_PCI_TPH_H
+
+#ifdef CONFIG_PCIE_TPH
+int pcie_tph_disable(struct pci_dev *dev);
+#else
+static inline int pcie_tph_disable(struct pci_dev *dev)
+{ return -EOPNOTSUPP; }
+#endif
+
+#endif /* LINUX_PCI_TPH_H */
diff --git a/include/linux/pci.h b/include/linux/pci.h
index d75a88ec5136..d88ebe87815a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1841,6 +1841,7 @@ static inline bool pci_aer_available(void) { return false; }
#endif

bool pci_ats_disabled(void);
+bool pci_tph_disabled(void);

#ifdef CONFIG_PCIE_PTM
int pci_enable_ptm(struct pci_dev *dev, u8 *granularity);
--
2.44.0