[PATCH 4/5] PCI/sysfs: Use user config accessors for link attributes

[Matthew Wood]

max_link_width, current_link_speed and current_link_width read the PCIe
Link Capabilities and Link Status registers with the kernel config
accessors. Those don't check block_cfg_access so a read that races
with a reset goes to the device mid-reset and can fail or return a bogus
value.

Use pcie_capability_user_read_{word,dword}() instead so the read waits for
any pci_cfg_access_lock() holder (e.g. pci_reset_function()) to finish. For
max_link_width, this means inlining the pcie_get_width_cap() logic
instead of creating an additional helper with this single calling location.

Signed-off-by: Matthew Wood <thepacketgeek@xxxxxxxxx>
Tested-by: Nikita Vetoshkin <nekto0n@xxxxxxxx>
---
 drivers/pci/pci-sysfs.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index b37a285d717d..a272f8583a8f 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -208,14 +208,16 @@ static ssize_t max_link_width_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	ssize_t ret;
+	u32 lnkcap;
 
 	/* We read PCI_EXP_LNKCAP, so we need the device to be accessible. */
 	pci_config_pm_runtime_get(pdev);
-	ret = sysfs_emit(buf, "%u\n", pcie_get_width_cap(pdev));
+	pcie_capability_user_read_dword(pdev, PCI_EXP_LNKCAP, &lnkcap);
 	pci_config_pm_runtime_put(pdev);
 
-	return ret;
+	return sysfs_emit(buf, "%u\n", lnkcap ?
+			  FIELD_GET(PCI_EXP_LNKCAP_MLW, lnkcap) :
+			  PCIE_LNK_WIDTH_UNKNOWN);
 }
 static DEVICE_ATTR_RO(max_link_width);
 
@@ -228,7 +230,8 @@ static ssize_t current_link_speed_show(struct device *dev,
 	enum pci_bus_speed speed;
 
 	pci_config_pm_runtime_get(pci_dev);
-	err = pcie_capability_read_word(pci_dev, PCI_EXP_LNKSTA, &linkstat);
+	err = pcie_capability_user_read_word(pci_dev, PCI_EXP_LNKSTA,
+					     &linkstat);
 	pci_config_pm_runtime_put(pci_dev);
 
 	if (err)
@@ -248,7 +251,8 @@ static ssize_t current_link_width_show(struct device *dev,
 	int err;
 
 	pci_config_pm_runtime_get(pci_dev);
-	err = pcie_capability_read_word(pci_dev, PCI_EXP_LNKSTA, &linkstat);
+	err = pcie_capability_user_read_word(pci_dev, PCI_EXP_LNKSTA,
+					     &linkstat);
 	pci_config_pm_runtime_put(pci_dev);
 
 	if (err)
-- 
2.53.0-Meta