[PATCH net-next] net: sfp: add debugfs support

* [PATCH net-next] net: sfp: add debugfs support
@ 2020-11-23 22:06 Russell King
  2020-11-24  0:14 ` Andrew Lunn
  0 siblings, 1 reply; 9+ messages in thread
From: Russell King @ 2020-11-23 22:06 UTC (permalink / raw)
  To: Andrew Lunn, Heiner Kallweit; +Cc: David S. Miller, netdev, Jakub Kicinski

Add debugfs support to SFP so that the internal state of the SFP state
machines and hardware signal state can be viewed from userspace, rather
than having to compile a debug kernel to view state state transitions
in the kernel log.  The 'state' output looks like:

Module state: empty
Module probe attempts: 0 0
Device state: up
Main state: down
Fault recovery remaining retries: 5
PHY probe remaining retries: 12
moddef0: 0
rx_los: 1
tx_fault: 1
tx_disable: 1

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
---
This is useful to view the state of the SFP cage when e.g., debugging
a module that the link doesn't seem to be coming up for. Rather than
sending this patch each time there is a query, it seems sensible to
merge it into mainline instead.

 drivers/net/phy/sfp.c | 55 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 1e347afa951e..2c32aa891f17 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/acpi.h>
 #include <linux/ctype.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/hwmon.h>
@@ -258,6 +259,9 @@ struct sfp {
 	char *hwmon_name;
 #endif
 
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+	struct dentry *debugfs_dir;
+#endif
 };
 
 static bool sff_module_supported(const struct sfp_eeprom_id *id)
@@ -1390,6 +1394,54 @@ static void sfp_module_tx_enable(struct sfp *sfp)
 	sfp_set_state(sfp, sfp->state);
 }
 
+#if IS_ENABLED(CONFIG_DEBUG_FS)
+static int sfp_debug_state_show(struct seq_file *s, void *data)
+{
+	struct sfp *sfp = s->private;
+
+	seq_printf(s, "Module state: %s\n",
+		   mod_state_to_str(sfp->sm_mod_state));
+	seq_printf(s, "Module probe attempts: %d %d\n",
+		   R_PROBE_RETRY_INIT - sfp->sm_mod_tries_init,
+		   R_PROBE_RETRY_SLOW - sfp->sm_mod_tries);
+	seq_printf(s, "Device state: %s\n",
+		   dev_state_to_str(sfp->sm_dev_state));
+	seq_printf(s, "Main state: %s\n",
+		   sm_state_to_str(sfp->sm_state));
+	seq_printf(s, "Fault recovery remaining retries: %d\n",
+		   sfp->sm_fault_retries);
+	seq_printf(s, "PHY probe remaining retries: %d\n",
+		   sfp->sm_phy_retries);
+	seq_printf(s, "moddef0: %d\n", !!(sfp->state & SFP_F_PRESENT));
+	seq_printf(s, "rx_los: %d\n", !!(sfp->state & SFP_F_LOS));
+	seq_printf(s, "tx_fault: %d\n", !!(sfp->state & SFP_F_TX_FAULT));
+	seq_printf(s, "tx_disable: %d\n", !!(sfp->state & SFP_F_TX_DISABLE));
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(sfp_debug_state);
+
+static void sfp_debugfs_init(struct sfp *sfp)
+{
+	sfp->debugfs_dir = debugfs_create_dir(dev_name(sfp->dev), NULL);
+
+	debugfs_create_file("state", 0600, sfp->debugfs_dir, sfp,
+			    &sfp_debug_state_fops);
+}
+
+static void sfp_debugfs_exit(struct sfp *sfp)
+{
+	debugfs_remove_recursive(sfp->debugfs_dir);
+}
+#else
+static void sfp_debugfs_init(struct sfp *sfp)
+{
+}
+
+static void sfp_debugfs_exit(struct sfp *sfp)
+{
+}
+#endif
+
 static void sfp_module_tx_fault_reset(struct sfp *sfp)
 {
 	unsigned int state = sfp->state;
@@ -2472,6 +2524,8 @@ static int sfp_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 
+	sfp_debugfs_init(sfp);
+
 	return 0;
 }
 
@@ -2479,6 +2533,7 @@ static int sfp_remove(struct platform_device *pdev)
 {
 	struct sfp *sfp = platform_get_drvdata(pdev);
 
+	sfp_debugfs_exit(sfp);
 	sfp_unregister_socket(sfp->sfp_bus);
 
 	rtnl_lock();
-- 
2.20.1


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