[PATCH v2 1/2] PCI: Avoid pointless capability searches

[Bjorn Helgaas <helgaas@kernel.org>]

From: Bjorn Helgaas <bhelgaas@google.com>

Many of the save/restore functions in the pci_save_state() and
pci_restore_state() paths depend on both a PCI capability of the device and
a pci_cap_saved_state structure to hold the configuration data, and they
skip the operation if either is missing.

Look for the pci_cap_saved_state first so if we don't have one, we can skip
searching for the device capability, which requires several slow config
space accesses.

Remove some error messages if the pci_cap_saved_state is not found so we
don't complain about having no saved state for a capability the device
doesn't have.  We have already warned in pci_allocate_cap_save_buffers() if
the capability is present but we were unable to allocate a buffer.

Other than the message change, no functional change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/pci/pci.c       | 27 ++++++++++++++-------------
 drivers/pci/pcie/aspm.c | 15 ++++++++-------
 2 files changed, 22 insertions(+), 20 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 869d204a70a3..503376bf7e75 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1686,10 +1686,8 @@ static int pci_save_pcie_state(struct pci_dev *dev)
 		return 0;
 
 	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
-	if (!save_state) {
-		pci_err(dev, "buffer not found in %s\n", __func__);
+	if (!save_state)
 		return -ENOMEM;
-	}
 
 	cap = (u16 *)&save_state->cap.data[0];
 	pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &cap[i++]);
@@ -1742,19 +1740,17 @@ static void pci_restore_pcie_state(struct pci_dev *dev)
 
 static int pci_save_pcix_state(struct pci_dev *dev)
 {
-	int pos;
 	struct pci_cap_saved_state *save_state;
+	u8 pos;
+
+	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX);
+	if (!save_state)
+		return -ENOMEM;
 
 	pos = pci_find_capability(dev, PCI_CAP_ID_PCIX);
 	if (!pos)
 		return 0;
 
-	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX);
-	if (!save_state) {
-		pci_err(dev, "buffer not found in %s\n", __func__);
-		return -ENOMEM;
-	}
-
 	pci_read_config_word(dev, pos + PCI_X_CMD,
 			     (u16 *)save_state->cap.data);
 
@@ -1763,14 +1759,19 @@ static int pci_save_pcix_state(struct pci_dev *dev)
 
 static void pci_restore_pcix_state(struct pci_dev *dev)
 {
-	int i = 0, pos;
 	struct pci_cap_saved_state *save_state;
+	u8 pos;
+	int i = 0;
 	u16 *cap;
 
 	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_PCIX);
-	pos = pci_find_capability(dev, PCI_CAP_ID_PCIX);
-	if (!save_state || !pos)
+	if (!save_state)
 		return;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_PCIX);
+	if (!pos)
+		return;
+
 	cap = (u16 *)&save_state->cap.data[0];
 
 	pci_write_config_word(dev, pos + PCI_X_CMD, cap[i++]);
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index e0bc90597dca..007e4a082e6f 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -35,16 +35,14 @@ void pci_save_ltr_state(struct pci_dev *dev)
 	if (!pci_is_pcie(dev))
 		return;
 
+	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
+	if (!save_state)
+		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);
@@ -57,8 +55,11 @@ void pci_restore_ltr_state(struct pci_dev *dev)
 	u32 *cap;
 
 	save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_LTR);
+	if (!save_state)
+		return;
+
 	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 */
-- 
2.34.1