[PATCH] pci: allow user specifiy a reset wait timeout

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

The spec does not provide any upper limit to how long a device may
return Request Retry Status. It just says "Some devices require a
lengthy self-initialization sequence to complete". The kernel
arbitrarily chose 60 seconds since that really ought to be enough. But
there are devices where this turns out not to be enough.

Since any timeout choice would be arbitrary, and 60 seconds is generally
more than enough for the majority of hardware, let's make this a
parameter so an admin can adjust it specifically to their needs if the
default timeout isn't appropriate.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 drivers/pci/pci.c                               | 6 +++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb8752b42ec85..1aed555ef8b40 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4843,6 +4843,9 @@
 
 				Note: this may remove isolation between devices
 				and may put more devices in an IOMMU group.
+		reset_wait=nn	The number of milliseconds to wait after a
+				reset while seeing Request Retry Status.
+				Default is 60000 (1 minute).
 		force_floating	[S390] Force usage of floating interrupts.
 		nomio		[S390] Do not use MIO instructions.
 		norid		[S390] ignore the RID field and force use of
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 869d204a70a37..20817dd5ebba7 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -75,7 +75,8 @@ struct pci_pme_device {
  * limit, but 60 sec ought to be enough for any device to become
  * responsive.
  */
-#define PCIE_RESET_READY_POLL_MS 60000 /* msec */
+#define PCIE_RESET_READY_POLL_MS pci_reset_ready_wait
+unsigned long pci_reset_ready_wait = 60000; /* msec */
 
 static void pci_dev_d3_sleep(struct pci_dev *dev)
 {
@@ -6841,6 +6842,9 @@ static int __init pci_setup(char *str)
 				disable_acs_redir_param = str + 18;
 			} else if (!strncmp(str, "config_acs=", 11)) {
 				config_acs_param = str + 11;
+			} else if (!strncmp(str, "reset_wait=", 11)) {
+				pci_reset_ready_wait =
+					simple_strtoul(str + 11, &str, 0);
 			} else {
 				pr_err("PCI: Unknown option `%s'\n", str);
 			}
-- 
2.43.5