From: Lukas Wunner <lukas@wunner.de>
Date: Sun, 3 May 2026 13:34:46 +0000 (+0200)
Subject: PCI: Drop unnecessary retries when restoring BARs
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=10baa9b4df4005ca53c59c30c2d4b774469e10b6;p=thirdparty%2Flinux.git

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 8228d2782f95..a21b0075e1de 100644
--- 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);
 	}
 }