linux-kernel - [PATCH v2 2/3] PCI/PTM: Implement pci_enable_ptm() for Root Ports, Switch Upstream Ports

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Message-Id: <20220902233543.390890-3-helgaas@kernel.org>
Date:   Fri,  2 Sep 2022 18:35:42 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Rajvi Jingar <rajvi.jingar@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>
Cc:     Koba Ko <koba.ko@...onical.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "David E . Box" <david.e.box@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH v2 2/3] PCI/PTM: Implement pci_enable_ptm() for Root Ports, Switch Upstream Ports

From: Bjorn Helgaas <bhelgaas@...gle.com>

Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/pcie/ptm.c | 34 +++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
index b6a417247ce3..ad283818f37b 100644
--- a/drivers/pci/pcie/ptm.c
+++ b/drivers/pci/pcie/ptm.c
@@ -167,11 +167,11 @@ int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
 	if (!pos)
 		return -EINVAL;
 
-	pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
-	if (!(cap & PCI_PTM_CAP_REQ))
-		return -EINVAL;
-
 	/*
+	 * Root Ports and Switch Upstream Ports have been configured
+	 * by pci_ptm_init(), so preserve their PCI_PTM_CTRL_ROOT and
+	 * granularity.
+	 *
 	 * For a PCIe Endpoint, PTM is only useful if the endpoint can
 	 * issue PTM requests to upstream devices that have PTM enabled.
 	 *
@@ -179,19 +179,39 @@ int pci_enable_ptm(struct pci_dev *dev, u8 *granularity)
 	 * device, so there must be some implementation-specific way to
 	 * associate the endpoint with a time source.
 	 */
-	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT) {
+	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
+	    pci_pcie_type(dev) == PCI_EXP_TYPE_UPSTREAM) {
+		if (pci_pcie_type(dev) == PCI_EXP_TYPE_UPSTREAM) {
+			ups = pci_upstream_bridge(dev);
+			if (!ups || !ups->ptm_enabled)
+				return -EINVAL;
+		}
+
+		pci_read_config_dword(dev, pos + PCI_PTM_CTRL, &ctrl);
+		ctrl |= PCI_PTM_CTRL_ENABLE;
+	} else if (pci_pcie_type(dev) == PCI_EXP_TYPE_ENDPOINT) {
+		pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
+		if (!(cap & PCI_PTM_CAP_REQ))
+			return -EINVAL;
+
 		ups = pci_upstream_bridge(dev);
 		if (!ups || !ups->ptm_enabled)
 			return -EINVAL;
 
 		dev->ptm_granularity = ups->ptm_granularity;
+		ctrl = PCI_PTM_CTRL_ENABLE;
+		ctrl |= dev->ptm_granularity << 8;
 	} else if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
+		pci_read_config_dword(dev, pos + PCI_PTM_CAP, &cap);
+		if (!(cap & PCI_PTM_CAP_REQ))
+			return -EINVAL;
+
 		dev->ptm_granularity = 0;
+		ctrl = PCI_PTM_CTRL_ENABLE;
+		ctrl |= dev->ptm_granularity << 8;
 	} else
 		return -EINVAL;
 
-	ctrl = PCI_PTM_CTRL_ENABLE;
-	ctrl |= dev->ptm_granularity << 8;
 	pci_write_config_dword(dev, pos + PCI_PTM_CTRL, ctrl);
 	dev->ptm_enabled = 1;
 
-- 
2.25.1