linux-kernel - [PATCH V1 1/9] PCI: Introduce PCIe TPH support framework

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Date: Thu, 9 May 2024 11:27:33 -0500
From: Wei Huang <wei.huang2@....com>
To: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <netdev@...r.kernel.org>
CC: <bhelgaas@...gle.com>, <corbet@....net>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<alex.williamson@...hat.com>, <gospo@...adcom.com>,
	<michael.chan@...adcom.com>, <ajit.khaparde@...adcom.com>,
	<manoj.panicker2@....com>, <Eric.VanTassell@....com>, <wei.huang2@....com>
Subject: [PATCH V1 1/9] PCI: Introduce PCIe TPH support framework

This patch implements the framework for PCIe TPH support. It introduces
tph.c source file, along with CONFIG_PCIE_TPH, to Linux PCIe subsystem.
A new member, named tph_cap, is also introduced in pci_dev to cache TPH
capability offset.

Co-developed-by: Eric Van Tassell <Eric.VanTassell@....com>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@....com>
Signed-off-by: Wei Huang <wei.huang2@....com>
---
 drivers/pci/pci.h         |  6 ++++++
 drivers/pci/pcie/Kconfig  | 10 ++++++++++
 drivers/pci/pcie/Makefile |  1 +
 drivers/pci/pcie/tph.c    | 28 ++++++++++++++++++++++++++++
 drivers/pci/probe.c       |  1 +
 include/linux/pci.h       |  4 ++++
 6 files changed, 50 insertions(+)
 create mode 100644 drivers/pci/pcie/tph.c

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 17fed1846847..6f1d35a68126 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -508,6 +508,12 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
 
 #endif /* CONFIG_PCI_IOV */
 
+#ifdef CONFIG_PCIE_TPH
+void pcie_tph_init(struct pci_dev *dev);
+#else
+static inline void pcie_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 8999fcebde6a..a4940e2af9b1 100644
--- a/drivers/pci/pcie/Kconfig
+++ b/drivers/pci/pcie/Kconfig
@@ -155,3 +155,13 @@ 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"
+	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..5f0cc06b74bb
--- /dev/null
+++ b/drivers/pci/pcie/tph.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TPH (TLP Processing Hints) support
+ *
+ * Copyright (C) 2024 Advanced Micro Devices, Inc.
+ *     Eric Van Tassell <Eric.VanTassell@....com>
+ *     Wei Huang <wei.huang2@....com>
+ */
+
+#define pr_fmt(fmt) "TPH: " fmt
+#define dev_fmt pr_fmt
+
+#include <linux/acpi.h>
+#include <uapi/linux/pci_regs.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/msi.h>
+#include <linux/pci.h>
+#include <linux/msi.h>
+#include <linux/pci-acpi.h>
+
+#include "../pci.h"
+
+void pcie_tph_init(struct pci_dev *dev)
+{
+	dev->tph_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_TPH);
+}
+
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 1325fbae2f28..9ac511032639 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2481,6 +2481,7 @@ 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 */
+	pcie_tph_init(dev);             /* TLP Processing Hints */
 
 	pcie_report_downtraining(dev);
 	pci_init_reset_methods(dev);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 16493426a04f..73d92c7d2c5b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -529,6 +529,10 @@ 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 */
+#endif
 };
 
 static inline struct pci_dev *pci_physfn(struct pci_dev *dev)
-- 
2.44.0