[PATCH 09/15] PCI/PTM: Save PTM state in the saved capability store

[David Matlack <dmatlack@google.com>]

Save and restore the PTM Control register through the per-device saved
capability store instead of a private pci_cap_saved_state buffer.

Report a reservation failure. pci_ptm_init() ignored the return value of
pci_add_ext_cap_save_buffer() entirely, so a failed allocation was only
noticed later as silently missing PTM state.

No functional change intended.

Assisted-by: LLM
Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/pcie/ptm.c | 29 ++++++-----------------------
 1 file changed, 6 insertions(+), 23 deletions(-)

diff --git a/drivers/pci/pcie/ptm.c b/drivers/pci/pcie/ptm.c
index bd3bd39f6372..a9e29e19b0f9 100644
--- a/drivers/pci/pcie/ptm.c
+++ b/drivers/pci/pcie/ptm.c
@@ -53,7 +53,8 @@ void pci_ptm_init(struct pci_dev *dev)
 
 	dev->ptm_cap = ptm;
 	atomic_set(&dev->ptm_enable_cnt, 0);
-	pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_PTM, sizeof(u32));
+	if (pci_reserve_saved_cap(dev, ptm + PCI_PTM_CTRL, sizeof(u32)))
+		pci_err(dev, "unable to reserve PTM save state\n");
 
 	pci_read_config_dword(dev, ptm + PCI_PTM_CAP, &cap);
 	dev->ptm_granularity = FIELD_GET(PCI_PTM_GRANULARITY_MASK, cap);
@@ -90,36 +91,18 @@ void pci_ptm_init(struct pci_dev *dev)
 
 void pci_save_ptm_state(struct pci_dev *dev)
 {
-	u16 ptm = dev->ptm_cap;
-	struct pci_cap_saved_state *save_state;
-	u32 *cap;
-
-	if (!ptm)
-		return;
-
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);
-	if (!save_state)
+	if (!dev->ptm_cap)
 		return;
 
-	cap = (u32 *)&save_state->cap.data[0];
-	pci_read_config_dword(dev, ptm + PCI_PTM_CTRL, cap);
+	pci_save_cap_dword(dev, dev->ptm_cap + PCI_PTM_CTRL);
 }
 
 void pci_restore_ptm_state(struct pci_dev *dev)
 {
-	u16 ptm = dev->ptm_cap;
-	struct pci_cap_saved_state *save_state;
-	u32 *cap;
-
-	if (!ptm)
-		return;
-
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_PTM);
-	if (!save_state)
+	if (!dev->ptm_cap)
 		return;
 
-	cap = (u32 *)&save_state->cap.data[0];
-	pci_write_config_dword(dev, ptm + PCI_PTM_CTRL, *cap);
+	pci_restore_cap_dword(dev, dev->ptm_cap + PCI_PTM_CTRL);
 }
 
 /* Enable PTM in the Control register if possible */
-- 
2.56.0.rc1.315.gc6ed9934b7-goog