PCI/ASPM: Move pci_save_ltr_state() to aspm.c

Even when CONFIG_PCIEASPM is not set, we save and restore the LTR
Capability so that if ASPM L1.2 and LTR were configured by the platform,
ASPM L1.2 will still work after suspend/resume, when that platform
configuration may be lost. See dbbfadf2 ("PCI/ASPM: Save LTR Capability
for suspend/resume").

Since ASPM L1.2 depends on the LTR Capability, move the save/restore code
to the part of aspm.c that is always compiled regardless of
CONFIG_PCIEASPM.  No functional change intended.
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20240128233212.1139663-5-david.e.box@linux.intel.com
[bhelgaas: commit log, reorder to make this a pure move]
Link: https://lore.kernel.org/r/20240223205851.114931-4-helgaas@kernel.orgSigned-off-by: David E. Box <david.e.box@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -1689,46 +1689,6 @@ static void pci_restore_pcix_state(struct pci_dev *dev)
 	pci_write_config_word(dev, pos + PCI_X_CMD, cap[i++]);
 }
 
-static void pci_save_ltr_state(struct pci_dev *dev)
-{
-	int ltr;
-	struct pci_cap_saved_state *save_state;
-	u32 *cap;
-
-	if (!pci_is_pcie(dev))
-		return;
-
-	ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
-	if (!ltr)
-		return;
-
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
-	if (!save_state) {
-		pci_err(dev, "no suspend buffer for LTR; ASPM issues possible after resume\n");
-		return;
-	}
-
-	/* Some broken devices only support dword access to LTR */
-	cap = &save_state->cap.data[0];
-	pci_read_config_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, cap);
-}
-
-static void pci_restore_ltr_state(struct pci_dev *dev)
-{
-	struct pci_cap_saved_state *save_state;
-	int ltr;
-	u32 *cap;
-
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
-	ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
-	if (!save_state || !ltr)
-		return;
-
-	/* Some broken devices only support dword access to LTR */
-	cap = &save_state->cap.data[0];
-	pci_write_config_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, *cap);
-}
-
 /**
  * pci_save_state - save the PCI configuration space of a device before
  *		    suspending

drivers/pci/pci.h

@@ -567,6 +567,11 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
 
 bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
 int pcie_retrain_link(struct pci_dev *pdev, bool use_lt);
+
+/* ASPM-related functionality we need even without CONFIG_PCIEASPM */
+void pci_save_ltr_state(struct pci_dev *dev);
+void pci_restore_ltr_state(struct pci_dev *dev);
+
 #ifdef CONFIG_PCIEASPM
 void pcie_aspm_init_link_state(struct pci_dev *pdev);
 void pcie_aspm_exit_link_state(struct pci_dev *pdev);

drivers/pci/pcie/aspm.c

@@ -24,6 +24,46 @@
 
 #include "../pci.h"
 
+void pci_save_ltr_state(struct pci_dev *dev)
+{
+	int ltr;
+	struct pci_cap_saved_state *save_state;
+	u32 *cap;
+
+	if (!pci_is_pcie(dev))
+		return;
+
+	ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
+	if (!ltr)
+		return;
+
+	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
+	if (!save_state) {
+		pci_err(dev, "no suspend buffer for LTR; ASPM issues possible after resume\n");
+		return;
+	}
+
+	/* Some broken devices only support dword access to LTR */
+	cap = &save_state->cap.data[0];
+	pci_read_config_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, cap);
+}
+
+void pci_restore_ltr_state(struct pci_dev *dev)
+{
+	struct pci_cap_saved_state *save_state;
+	int ltr;
+	u32 *cap;
+
+	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
+	ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
+	if (!save_state || !ltr)
+		return;
+
+	/* Some broken devices only support dword access to LTR */
+	cap = &save_state->cap.data[0];
+	pci_write_config_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, *cap);
+}
+
 #ifdef CONFIG_PCIEASPM
 
 #ifdef MODULE_PARAM_PREFIX