[PATCH 08/15] PCI/AER: Save AER state in the saved capability store

[David Matlack <dmatlack@google.com>]

Save and restore the AER mask, severity, capability and root command
registers through the per-device saved capability store instead of a
private pci_cap_saved_state buffer.

Describe the registers in aer_saved_regs[] and drive the reservation, save,
and restore loops from it. Previously the three had to be kept in the same
order by hand, and pci_aer_init() encoded the register count as a bare 4 or
5.

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

No functional change intended.

Assisted-by: LLM
Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/pcie/aer.c | 79 +++++++++++++++++++++---------------------
 1 file changed, 40 insertions(+), 39 deletions(-)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index d8dcd238fda1..765899cf4046 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -352,53 +352,53 @@ int pci_aer_clear_status(struct pci_dev *dev)
 	return pci_aer_raw_clear_status(dev);
 }
 
-void pci_save_aer_state(struct pci_dev *dev)
+/*
+ * AER registers saved and restored by the PCI core. PCI_ERR_ROOT_COMMAND is
+ * only implemented by Root Ports and Root Complex Event Collectors (PCIe
+ * r6.0, sec 7.8.4.9) and so must come last.
+ */
+static const u16 aer_saved_regs[] = {
+	PCI_ERR_UNCOR_MASK,
+	PCI_ERR_UNCOR_SEVER,
+	PCI_ERR_COR_MASK,
+	PCI_ERR_CAP,
+	PCI_ERR_ROOT_COMMAND,
+};
+
+static unsigned int aer_nr_saved_regs(struct pci_dev *dev)
 {
-	int aer = dev->aer_cap;
-	struct pci_cap_saved_state *save_state;
-	u32 *cap;
+	if (pcie_cap_has_rtctl(dev))
+		return ARRAY_SIZE(aer_saved_regs);
 
-	if (!aer)
-		return;
+	return ARRAY_SIZE(aer_saved_regs) - 1;
+}
+
+void pci_save_aer_state(struct pci_dev *dev)
+{
+	unsigned int i;
 
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_ERR);
-	if (!save_state)
+	if (!dev->aer_cap)
 		return;
 
-	cap = &save_state->cap.data[0];
-	pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, cap++);
-	pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_SEVER, cap++);
-	pci_read_config_dword(dev, aer + PCI_ERR_COR_MASK, cap++);
-	pci_read_config_dword(dev, aer + PCI_ERR_CAP, cap++);
-	if (pcie_cap_has_rtctl(dev))
-		pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, cap++);
+	for (i = 0; i < aer_nr_saved_regs(dev); i++)
+		pci_save_cap_dword(dev, dev->aer_cap + aer_saved_regs[i]);
 }
 
 void pci_restore_aer_state(struct pci_dev *dev)
 {
-	int aer = dev->aer_cap;
-	struct pci_cap_saved_state *save_state;
-	u32 *cap;
+	unsigned int i;
 
-	if (!aer)
-		return;
-
-	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_ERR);
-	if (!save_state)
+	if (!dev->aer_cap)
 		return;
 
-	cap = &save_state->cap.data[0];
-	pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, *cap++);
-	pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_SEVER, *cap++);
-	pci_write_config_dword(dev, aer + PCI_ERR_COR_MASK, *cap++);
-	pci_write_config_dword(dev, aer + PCI_ERR_CAP, *cap++);
-	if (pcie_cap_has_rtctl(dev))
-		pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, *cap++);
+	for (i = 0; i < aer_nr_saved_regs(dev); i++)
+		pci_restore_cap_dword(dev, dev->aer_cap + aer_saved_regs[i]);
 }
 
 void pci_aer_init(struct pci_dev *dev)
 {
-	int n;
+	unsigned int i;
+	int error;
 
 	dev->aer_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
 	if (!dev->aer_cap)
@@ -415,14 +415,15 @@ void pci_aer_init(struct pci_dev *dev)
 	ratelimit_state_init(&dev->aer_info->nonfatal_ratelimit,
 			     DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
 
-	/*
-	 * We save/restore PCI_ERR_UNCOR_MASK, PCI_ERR_UNCOR_SEVER,
-	 * PCI_ERR_COR_MASK, and PCI_ERR_CAP.  Root and Root Complex Event
-	 * Collectors also implement PCI_ERR_ROOT_COMMAND (PCIe r6.0, sec
-	 * 7.8.4.9).
-	 */
-	n = pcie_cap_has_rtctl(dev) ? 5 : 4;
-	pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_ERR, sizeof(u32) * n);
+	for (i = 0; i < aer_nr_saved_regs(dev); i++) {
+		unsigned int off = dev->aer_cap + aer_saved_regs[i];
+
+		error = pci_reserve_saved_cap(dev, off, sizeof(u32));
+		if (error) {
+			pci_err(dev, "unable to reserve AER save state\n");
+			break;
+		}
+	}
 
 	/*
 	 * Advisory Non-Fatal Errors are masked by default (PCIe r7.0, sec
-- 
2.56.0.rc1.315.gc6ed9934b7-goog