Save and restore the LTR maximum latency registers through the per-device
saved capability store instead of a private pci_cap_saved_state buffer.

Reserve the DWORD by its configuration space offset during device setup,
in pci_reserve_ltr_state(), and keep accessing the registers a DWORD at
a time because some devices only support DWORD access to them.

No functional change intended.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/pci.c       |  8 +-------
 drivers/pci/pci.h       |  1 +
 drivers/pci/pcie/aspm.c | 31 ++++++++++++++++---------------
 3 files changed, 18 insertions(+), 22 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6cf4a64cb7e6..29d9474db1ae 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3742,15 +3742,9 @@ int pci_add_ext_cap_save_buffer(struct pci_dev *dev, u16 cap, unsigned int size)
  */
 void pci_allocate_cap_save_buffers(struct pci_dev *dev)
 {
-	int error;
-
 	pci_reserve_pcie_state(dev);
 	pci_reserve_pcix_state(dev);
-
-	error = pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_LTR,
-					    2 * sizeof(u16));
-	if (error)
-		pci_err(dev, "unable to allocate suspend buffer for LTR\n");
+	pci_reserve_ltr_state(dev);
 
 	pci_allocate_acs_save_buffer(dev);
 	pci_allocate_vc_save_buffers(dev);
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 206e0d04e06e..0daa2439db5e 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -1151,6 +1151,7 @@ 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_reserve_ltr_state(struct pci_dev *dev);
 void pci_restore_ltr_state(struct pci_dev *dev);
 void pci_configure_aspm_l1ss(struct pci_dev *dev);
 void pci_save_aspm_l1ss_state(struct pci_dev *dev);
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 02922b887ec6..39adf2cad331 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -30,8 +30,6 @@
 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;
@@ -40,31 +38,34 @@ void pci_save_ltr_state(struct pci_dev *dev)
 	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");
+	/* Some broken devices only support dword access to LTR */
+	pci_save_cap_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT);
+}
+
+void pci_reserve_ltr_state(struct pci_dev *dev)
+{
+	int ltr, rc;
+
+	ltr = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
+	if (!ltr)
 		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);
+	rc = pci_reserve_saved_cap(dev, ltr + PCI_LTR_MAX_SNOOP_LAT, sizeof(u32));
+	if (rc)
+		pci_err(dev, "unable to reserve LTR save state (%pe)\n",
+			ERR_PTR(rc));
 }
 
 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)
+	if (!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_restore_cap_dword(dev, ltr + PCI_LTR_MAX_SNOOP_LAT);
 }
 
 void pci_configure_aspm_l1ss(struct pci_dev *pdev)
-- 
2.56.0.455.g6c5a503b38-goog