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Message-Id: <20250208050329.1092214-2-helgaas@kernel.org>
Date: Fri, 7 Feb 2025 23:03:28 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Alex Williamson <alex.williamson@...hat.com>,
Christian König <ckoenig.leichtzumerken@...il.com>
Cc: linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org,
Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH 1/2] PCI: Avoid pointless capability searches
From: Bjorn Helgaas <bhelgaas@...gle.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@...gle.com>
---
drivers/pci/pci.c | 27 ++++++++++++++-------------
drivers/pci/pcie/aspm.c | 15 ++++++++-------
drivers/pci/vc.c | 22 +++++++++++-----------
3 files changed, 33 insertions(+), 31 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 */
diff --git a/drivers/pci/vc.c b/drivers/pci/vc.c
index a4ff7f5f66dd..c39f3be518d4 100644
--- a/drivers/pci/vc.c
+++ b/drivers/pci/vc.c
@@ -355,20 +355,17 @@ int pci_save_vc_state(struct pci_dev *dev)
int i;
for (i = 0; i < ARRAY_SIZE(vc_caps); i++) {
- int pos, ret;
struct pci_cap_saved_state *save_state;
+ int pos, ret;
+
+ save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id);
+ if (!save_state)
+ return -ENOMEM;
pos = pci_find_ext_capability(dev, vc_caps[i].id);
if (!pos)
continue;
- save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id);
- if (!save_state) {
- pci_err(dev, "%s buffer not found in %s\n",
- vc_caps[i].name, __func__);
- return -ENOMEM;
- }
-
ret = pci_vc_do_save_buffer(dev, pos, save_state, true);
if (ret) {
pci_err(dev, "%s save unsuccessful %s\n",
@@ -392,12 +389,15 @@ void pci_restore_vc_state(struct pci_dev *dev)
int i;
for (i = 0; i < ARRAY_SIZE(vc_caps); i++) {
- int pos;
struct pci_cap_saved_state *save_state;
+ int pos;
+
+ save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id);
+ if (!save_state)
+ continue;
pos = pci_find_ext_capability(dev, vc_caps[i].id);
- save_state = pci_find_saved_ext_cap(dev, vc_caps[i].id);
- if (!save_state || !pos)
+ if (!pos)
continue;
pci_vc_do_save_buffer(dev, pos, save_state, false);
--
2.34.1
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