PCI: Drop unnecessary retries when restoring BARs

In 2012, commit 26f41062f28d ("PCI: check for pci bar restore completion
and retry") amended pci_restore_state() to attempt BAR restoration up to 10
times.  This was necessary because back in the day, only a 100 msec delay
was observed after pcie_flr() carried out a Function Level Reset.  The
retries ensured that BARs were restored even if devices needed more time to
come out of reset.

In 2016, commit 5adecf817dd6 ("PCI: Wait for up to 1000ms after FLR reset")
extended the delay to 1 sec.  Commit a2758b6b8fdb ("PCI: Rename
pci_flr_wait() to pci_dev_wait() and make it generic") subsequently
extended it further to 60 sec.

The lengthened delay makes it unnecessary to retry BAR restoration, so
drop it.

Reported-by: Bjorn Helgaas <bhelgaas@google.com>
Closes: https://lore.kernel.org/r/20260416225745.GA41850@bhelgaas/
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/785c98b50a7a00d0698848c75d51b8f5669ad18f.1777814679.git.lukas@wunner.de

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 8228d2782f9590c62aafe1b0f95f7bb728b8982b..a21b0075e1dee9535bed152c90d6c45154c798b6 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1784,7 +1784,7 @@ int pci_save_state(struct pci_dev *dev)
 EXPORT_SYMBOL(pci_save_state);
 
 static void pci_restore_config_dword(struct pci_dev *pdev, int offset,
-                                    u32 saved_val, int retry, bool force)
+                                    u32 saved_val, bool force)
 {
        u32 val;
 
@@ -1792,52 +1792,42 @@ static void pci_restore_config_dword(struct pci_dev *pdev, int offset,
        if (!force && val == saved_val)
                return;
 
-       for (;;) {
-               pci_dbg(pdev, "restore config %#04x: %#010x -> %#010x\n",
-                       offset, val, saved_val);
-               pci_write_config_dword(pdev, offset, saved_val);
-               if (retry-- <= 0)
-                       return;
+       pci_dbg(pdev, "restore config %#04x: %#010x -> %#010x\n", offset, val,
+               saved_val);
 
-               pci_read_config_dword(pdev, offset, &val);
-               if (val == saved_val)
-                       return;
-
-               mdelay(1);
-       }
+       pci_write_config_dword(pdev, offset, saved_val);
 }
 
 static void pci_restore_config_space_range(struct pci_dev *pdev,
-                                          int start, int end, int retry,
-                                          bool force)
+                                          int start, int end, bool force)
 {
        int index;
 
        for (index = end; index >= start; index--)
                pci_restore_config_dword(pdev, 4 * index,
                                         pdev->saved_config_space[index],
-                                        retry, force);
+                                        force);
 }
 
 static void pci_restore_config_space(struct pci_dev *pdev)
 {
        if (pdev->hdr_type == PCI_HEADER_TYPE_NORMAL) {
-               pci_restore_config_space_range(pdev, 10, 15, 0, false);
+               pci_restore_config_space_range(pdev, 10, 15, false);
                /* Restore BARs before the command register. */
-               pci_restore_config_space_range(pdev, 4, 9, 10, false);
-               pci_restore_config_space_range(pdev, 0, 3, 0, false);
+               pci_restore_config_space_range(pdev, 4, 9, false);
+               pci_restore_config_space_range(pdev, 0, 3, false);
        } else if (pdev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
-               pci_restore_config_space_range(pdev, 12, 15, 0, false);
+               pci_restore_config_space_range(pdev, 12, 15, false);
 
                /*
                 * Force rewriting of prefetch registers to avoid S3 resume
                 * issues on Intel PCI bridges that occur when these
                 * registers are not explicitly written.
                 */
-               pci_restore_config_space_range(pdev, 9, 11, 0, true);
-               pci_restore_config_space_range(pdev, 0, 8, 0, false);
+               pci_restore_config_space_range(pdev, 9, 11, true);
+               pci_restore_config_space_range(pdev, 0, 8, false);
        } else {
-               pci_restore_config_space_range(pdev, 0, 15, 0, false);
+               pci_restore_config_space_range(pdev, 0, 15, false);
        }
 }