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

Key the save and restore paths off pdev->dpc_cap rather than
pci_is_pcie(). The old code relied on the save buffer existing only when
the capability did, and the store has no per-capability entry to check.

Reserve the register in pci_reserve_dpc_state(), called from
pci_dpc_init().

No functional change intended.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/pcie/dpc.c | 37 +++++++++++++++----------------------
 1 file changed, 15 insertions(+), 22 deletions(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index b7f79266f66d..16203e9ef240 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -45,34 +45,18 @@ static const char * const rp_pio_error_string[] = {
 
 void pci_save_dpc_state(struct pci_dev *dev)
 {
-	struct pci_cap_saved_state *save_state;
-	u16 *cap;
-
-	if (!pci_is_pcie(dev))
-		return;
-
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_DPC);
-	if (!save_state)
+	if (!dev->dpc_cap)
 		return;
 
-	cap = (u16 *)&save_state->cap.data[0];
-	pci_read_config_word(dev, dev->dpc_cap + PCI_EXP_DPC_CTL, cap);
+	pci_save_cap_word(dev, dev->dpc_cap + PCI_EXP_DPC_CTL);
 }
 
 void pci_restore_dpc_state(struct pci_dev *dev)
 {
-	struct pci_cap_saved_state *save_state;
-	u16 *cap;
-
-	if (!pci_is_pcie(dev))
-		return;
-
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_DPC);
-	if (!save_state)
+	if (!dev->dpc_cap)
 		return;
 
-	cap = (u16 *)&save_state->cap.data[0];
-	pci_write_config_word(dev, dev->dpc_cap + PCI_EXP_DPC_CTL, *cap);
+	pci_restore_cap_word(dev, dev->dpc_cap + PCI_EXP_DPC_CTL);
 }
 
 static DECLARE_WAIT_QUEUE_HEAD(dpc_completed_waitqueue);
@@ -400,6 +384,16 @@ static irqreturn_t dpc_irq(int irq, void *context)
 	return IRQ_HANDLED;
 }
 
+static void pci_reserve_dpc_state(struct pci_dev *pdev)
+{
+	int rc;
+
+	rc = pci_reserve_saved_cap(pdev, pdev->dpc_cap + PCI_EXP_DPC_CTL, sizeof(u16));
+	if (rc)
+		pci_err(pdev, "unable to reserve DPC save state (%pe)\n",
+			ERR_PTR(rc));
+}
+
 void pci_dpc_init(struct pci_dev *pdev)
 {
 	u16 cap;
@@ -408,8 +402,7 @@ void pci_dpc_init(struct pci_dev *pdev)
 	if (!pdev->dpc_cap)
 		return;
 
-	if (pci_add_ext_cap_save_buffer(pdev, PCI_EXT_CAP_ID_DPC, sizeof(u16)))
-		pci_err(pdev, "unable to allocate suspend buffer for DPC\n");
+	pci_reserve_dpc_state(pdev);
 
 	pci_read_config_word(pdev, pdev->dpc_cap + PCI_EXP_DPC_CAP, &cap);
 	if (!(cap & PCI_EXP_DPC_CAP_RP_EXT))
-- 
2.56.0.455.g6c5a503b38-goog