netdev - [RFC PATCH net-next 06/12] PCI: Add debug print for device ready delay

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Message-ID: <20231017074257.3389177-7-idosch@nvidia.com>
Date: Tue, 17 Oct 2023 10:42:51 +0300
From: Ido Schimmel <idosch@...dia.com>
To: <netdev@...r.kernel.org>, <linux-pci@...r.kernel.org>
CC: <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<edumazet@...gle.com>, <bhelgaas@...gle.com>, <alex.williamson@...hat.com>,
	<lukas@...ner.de>, <petrm@...dia.com>, <jiri@...dia.com>, <mlxsw@...dia.com>,
	Ido Schimmel <idosch@...dia.com>
Subject: [RFC PATCH net-next 06/12] PCI: Add debug print for device ready delay

Currently, the time it took a PCI device to become ready after reset is
only printed if it was longer than 1000ms ('PCI_RESET_WAIT'). However,
for debugging purposes it is useful to know this time even if it was
shorter. For example, with the device I am working on, hardware
engineers asked to verify that it becomes ready on the first try (no
delay).

To that end, add a debug level print that can be enabled using dynamic
debug. Example:

 # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/reset
 # dmesg -c | grep ready
 # echo "file drivers/pci/pci.c +p" > /sys/kernel/debug/dynamic_debug/control
 # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/reset
 # dmesg -c | grep ready
 [  396.060335] mlxsw_spectrum4 0000:01:00.0: ready 0ms after link toggle
 # echo "file drivers/pci/pci.c -p" > /sys/kernel/debug/dynamic_debug/control
 # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/reset
 # dmesg -c | grep ready

Signed-off-by: Ido Schimmel <idosch@...dia.com>
---
 drivers/pci/pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 59c01d68c6d5..0a708e65c5c4 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1216,6 +1216,9 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
 	if (delay > PCI_RESET_WAIT)
 		pci_info(dev, "ready %dms after %s\n", delay - 1,
 			 reset_type);
+	else
+		pci_dbg(dev, "ready %dms after %s\n", delay - 1,
+			reset_type);
 
 	return 0;
 }
-- 
2.40.1