linux-kernel - [PATCH 2/5] PCI: Create function to save L1SS offset

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Date: Sun, 28 Jan 2024 15:32:09 -0800
From: "David E. Box" <david.e.box@...ux.intel.com>
To: mika.westerberg@...ux.intel.com,
	david.e.box@...ux.intel.com,
	ilpo.jarvinen@...ux.intel.com,
	bhelgaas@...gle.com,
	rjw@...ysocki.net
Cc: tasev.stefanoska@...net.be,
	enriquezmark36@...il.com,
	kernel@...t.link,
	wse@...edocomputers.com,
	vidyas@...dia.com,
	kai.heng.feng@...onical.com,
	sathyanarayanan.kuppuswamy@...ux.intel.com,
	ricky_wu@...ltek.com,
	mario.limonciello@....com,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/5] PCI: Create function to save L1SS offset

The offset for the L1 Substate Capability register is not saved in pci_dev
until pci_configure_ltr() which only builds with CONFIG_PCIEASPM. Instead,
create a separate function to retrieve the offset so that it is always
available. This offset will be used to save and restore the L1SS registers
even when PCIEASPM=n.

Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
---
 drivers/pci/pci.h       | 1 +
 drivers/pci/pcie/aspm.c | 9 ++++++---
 drivers/pci/probe.c     | 1 +
 include/linux/pci.h     | 4 ++--
 4 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 6771862de921..b48e8e4f360f 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -97,6 +97,7 @@ void pci_msi_init(struct pci_dev *dev);
 void pci_msix_init(struct pci_dev *dev);
 bool pci_bridge_d3_possible(struct pci_dev *dev);
 void pci_bridge_d3_update(struct pci_dev *dev);
+void pci_aspm_get_l1ss(struct pci_dev *pdev);
 int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type);
 
 static inline void pci_wakeup_event(struct pci_dev *dev)
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 6d077e237a65..93718b733af3 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -24,6 +24,12 @@
 
 #include "../pci.h"
 
+void pci_aspm_get_l1ss(struct pci_dev *pdev)
+{
+	/* Read L1 PM substate capabilities */
+	pdev->l1ss = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_L1SS);
+}
+
 #ifdef CONFIG_PCIEASPM
 
 #ifdef MODULE_PARAM_PREFIX
@@ -970,9 +976,6 @@ void pci_configure_ltr(struct pci_dev *pdev)
 	if (!pci_is_pcie(pdev))
 		return;
 
-	/* Read L1 PM substate capabilities */
-	pdev->l1ss = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_L1SS);
-
 	pcie_capability_read_dword(pdev, PCI_EXP_DEVCAP2, &cap);
 	if (!(cap & PCI_EXP_DEVCAP2_LTR))
 		return;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 0b8c2c9cc9dd..e39ad912ce8c 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2208,6 +2208,7 @@ static void pci_configure_device(struct pci_dev *dev)
 	pci_configure_mps(dev);
 	pci_configure_extended_tags(dev, NULL);
 	pci_configure_relaxed_ordering(dev);
+	pci_aspm_get_l1ss(dev);
 	pci_configure_ltr(dev);
 	pci_configure_eetlp_prefix(dev);
 	pci_configure_serr(dev);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index dea043bc1e38..dfc4b525c7a1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -390,9 +390,9 @@ struct pci_dev {
 	unsigned int	d3hot_delay;	/* D3hot->D0 transition time in ms */
 	unsigned int	d3cold_delay;	/* D3cold->D0 transition time in ms */
 
-#ifdef CONFIG_PCIEASPM
-	struct pcie_link_state	*link_state;	/* ASPM link state */
 	u16		l1ss;		/* L1SS Capability pointer */
+#ifdef CONFIG_PCIEASPM
+	struct pcie_link_state	*link_state;	/* ASPM link state */
 	unsigned int	ltr_path:1;	/* Latency Tolerance Reporting
 					   supported from root to here */
 #endif
-- 
2.34.1